Lab result explainedInflammationLast updated November 10, 2026

IgG blood test: what high and low immunoglobulin G levels mean

Immunoglobulin G (IgG) · Quantitative immunoglobulins (IgG, IgA, IgM); sometimes with IgG subclasses or serum protein electrophoresis · reported in mg/dL (outside the US, g/L; 1 g/L = 100 mg/dL)

Immunoglobulin G (IgG) is the most abundant antibody in your blood, making up about three-quarters of all circulating antibody and about 10 to 20 percent of total plasma protein. Plasma cells produce it after the immune system has met a germ or vaccine, and it is the antibody of long-term memory: IgG against measles or hepatitis B persists for decades and is what a 'positive IgG' on an infection test refers to. A total IgG blood test measures the whole pool, regardless of what each antibody targets. For adults the normal range is roughly 700 to 1,600 mg/dL (7 to 16 g/L), with some variation between laboratories and lower values in children.

Low IgG (hypogammaglobulinemia) is the result that matters most clinically, because too little antibody means recurrent bacterial infections of the sinuses, ears and lungs. It can be inherited (common variable immunodeficiency and rarer primary immunodeficiencies) or, far more often, secondary to medications such as steroids and rituximab, to protein loss through the kidneys or gut, or to blood cancers. A high IgG is usually a response to something chronic (infection, autoimmune disease, liver disease) and is polyclonal, meaning thousands of different antibodies have risen together; the important exception is a monoclonal rise from a single plasma-cell clone, as in MGUS and multiple myeloma, which only protein electrophoresis can distinguish.

IgG is usually ordered as part of quantitative immunoglobulins with IgA and IgM, and the pattern across the three is as informative as any single value. All three low points to a global antibody deficiency; one very high with the others low or normal points to a monoclonal protein; all three high points to chronic polyclonal stimulation. IgG subclasses (IgG1 to IgG4) are a separate test ordered when total IgG is normal but infections or a specific condition such as IgG4-related disease are suspected.

IgG at a glance

  • What it is: the main antibody class in blood, made by plasma cells; provides long-term protection after infection and vaccination and crosses the placenta to protect newborns.
  • Normal (adults): about 700–1,600 mg/dL (7–16 g/L). Infants are lowest at 3 to 6 months; adult levels are reached by the mid-teens. Labs differ.
  • Low IgG: under about 600–700 mg/dL; under about 400–450 mg/dL with low IgA or IgM and poor vaccine responses defines common variable immunodeficiency; under 200 mg/dL is severe.
  • High IgG: chronic infection, autoimmune disease, chronic liver disease, HIV, sarcoidosis or IgG4-related disease (polyclonal); or MGUS or multiple myeloma (monoclonal), told apart by serum protein electrophoresis.
  • IgG vs IgM on an infection test: IgM means recent infection (appears within 1 to 2 weeks, fades over months); IgG means past infection or vaccination and usually lasts years.
  • Next step: for low IgG, IgA and IgM, vaccine antibody titers, a medication review and a search for protein loss or blood cancer; for high IgG, protein electrophoresis with immunofixation, free light chains, and tests for the suspected chronic cause.

Have your whole report? Paste it into the free Lab Explainer

Every marker explained in plain language, in context with the others, with questions to bring to your appointment. No account needed.

What IgG measures

IgG is a Y-shaped protein of about 150 kilodaltons made of two heavy and two light chains. The tips of the Y bind a specific target (a bacterial surface, a toxin, a virus), and the stem activates complement and recruits phagocytes and natural killer cells to destroy whatever is bound. Each plasma cell makes IgG against one target, so the total IgG level is the sum of millions of different antibodies; a rise or fall in the total reflects the overall activity or capacity of the antibody-producing system rather than immunity to any one thing.

The lab measures total IgG by nephelometry or turbidimetry, in which anti-IgG antibodies clump the IgG in the sample and the cloudiness is read optically, reported in mg/dL in the US and g/L elsewhere (divide mg/dL by 100). The four subclasses are measured separately when ordered: IgG1 is about 60 to 70 percent of the total and responds to proteins and viruses, IgG2 about 20 to 30 percent and responds to bacterial capsule polysaccharides, IgG3 about 5 to 8 percent, and IgG4 under 5 percent, rising with repeated antigen exposure and in IgG4-related disease.

IgG has a half-life of about 21 to 23 days, the longest of any antibody, which is why levels change slowly: a drug that stops production takes weeks to months to lower IgG, and infused immunoglobulin lasts about a month. The test does not need fasting. Levels are modestly lower in pregnancy (dilution and transfer to the fetus), a few percent lower after lying down for a long period, and can be transiently raised for weeks after an infusion of intravenous immunoglobulin.

Normal range for IgG

Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.

GroupTypical range (mg/dL (outside the US, g/L; 1 g/L = 100 mg/dL))Notes
AdultsAbout 700–1,600 mg/dL (7–16 g/L)Labs differ; some quote 600–1,640 or 650–1,500 mg/dL. Values are slightly higher in women and rise a little with age.
Newborn (cord blood)About 650–1,600 mg/dL, all maternal IgGMaternal antibody fades over 3 to 6 months while the infant's own production starts.
Infants 3–6 months (physiological low point)About 200–700 mg/dLThe nadir of 'physiological hypogammaglobulinemia'; premature infants dip lower.
Children 1–10 yearsAbout 400–1,200 mg/dL, rising with ageAdult levels are reached by about 12 to 16 years. Pediatric labs use age-specific ranges.
Mild to moderate low IgGAbout 400–700 mg/dLOften from medications or protein loss; evaluated when infections are frequent or other immunoglobulins are also low.
Severe low IgGBelow about 200–400 mg/dLHigh infection risk; immunoglobulin replacement is usually considered when there are recurrent infections, with a target trough above about 500–800 mg/dL.
Polyclonal high IgG1,600–3,000 mg/dL, occasionally higherChronic infection, autoimmune or liver disease; electrophoresis shows a broad band, not a spike.
Monoclonal IgG (M-protein)MGUS: M-protein under 3,000 mg/dL (3 g/dL); smoldering or active myeloma: 3,000 mg/dL or more, or any level with organ damageDefined by electrophoresis and immunofixation, not by the total IgG. Hyperviscosity is rare with IgG unless very high.
IgG4 subclassNormal under about 125–135 mg/dLAbove 135 mg/dL supports IgG4-related disease but also occurs in about 5 percent of healthy people and in allergy, infection and cancer.

High IgG

A high total IgG means the antibody-producing system is being driven harder than usual. The crucial question is whether the rise is polyclonal (thousands of different plasma-cell clones all making more antibody, in response to a chronic stimulus) or monoclonal (one abnormal clone making a single identical antibody). The total IgG cannot tell these apart; serum protein electrophoresis can, showing a broad, diffuse gamma band for polyclonal rises and a sharp spike (M-protein or paraprotein) for a monoclonal one, which immunofixation then types. For this reason an unexplained high IgG is almost always followed by electrophoresis.

Polyclonal rises, which account for the great majority, come from chronic infections (HIV, hepatitis C, tuberculosis, endocarditis, osteomyelitis), autoimmune diseases (lupus, rheumatoid arthritis, Sjögren's, autoimmune hepatitis, where IgG above about 1.1 times the upper limit is part of the diagnostic score), chronic liver disease of any cause, sarcoidosis, and IgG4-related disease. Values of 1,600 to 3,000 mg/dL are typical and the level loosely tracks disease activity. In a large series of people with polyclonal gammopathy, liver disease, connective tissue disease, chronic infection and blood cancers together explained most cases.

A monoclonal IgG is found in about 3 percent of people over 50 and 5 percent over 70, nearly always as monoclonal gammopathy of undetermined significance (MGUS), a premalignant state that progresses to myeloma or a related disorder at about 1 percent per year. An M-protein under 3,000 mg/dL with no anemia, kidney impairment, high calcium or bone lesions is MGUS and is simply monitored; 3,000 mg/dL or more, or more than 10 percent plasma cells in the marrow, is smoldering myeloma, and any level with organ damage is active myeloma. Very high IgG (usually above 4,000 to 6,000 mg/dL) can thicken the blood enough to cause hyperviscosity symptoms, though this is much more common with IgM.

Common causes

  1. Chronic infection

    HIV (often 2,000 to 3,000 mg/dL), chronic hepatitis B or C, tuberculosis, infective endocarditis, osteomyelitis, chronic sinusitis or bronchiectasis, and parasitic infections such as malaria and visceral leishmaniasis all drive sustained polyclonal IgG production.

  2. Autoimmune and connective tissue disease

    Systemic lupus, rheumatoid arthritis, Sjögren's syndrome, systemic sclerosis, mixed connective tissue disease and vasculitis commonly raise IgG, in rough proportion to activity. Sjögren's produces some of the highest polyclonal values.

  3. Chronic liver disease, especially autoimmune hepatitis

    Cirrhosis of any cause raises immunoglobulins as gut bacterial antigens bypass the liver; autoimmune hepatitis specifically raises IgG, and an IgG above the upper limit is one of the diagnostic criteria. Alcohol-related liver disease raises IgA more than IgG.

  4. Monoclonal gammopathy of undetermined significance (MGUS)

    A single plasma-cell clone producing an IgG M-protein under 3 g/dL with no organ damage; present in 3 percent of people over 50. Progresses to myeloma or related disease at about 1 percent a year, so it is monitored with periodic electrophoresis.

  5. Multiple myeloma

    IgG myeloma is the commonest type (about 50 to 60 percent of cases). The M-protein is often above 3,000 mg/dL, other immunoglobulins are suppressed, and there is anemia, kidney impairment, high calcium or bone pain. Free light chains and a marrow biopsy confirm it.

  6. IgG4-related disease

    A fibro-inflammatory condition affecting the pancreas, salivary and lacrimal glands, bile ducts, kidneys, aorta and retroperitoneum. Serum IgG4 is above 135 mg/dL in about 70 to 90 percent of patients, often with a raised total IgG; biopsy confirms the diagnosis.

  7. Sarcoidosis and other granulomatous disease

    Hypergammaglobulinemia occurs in 30 to 80 percent of people with sarcoidosis, alongside raised ACE and calcium in some.

  8. Lymphoma, chronic lymphocytic leukemia and Castleman disease

    Can raise IgG polyclonally through cytokine (IL-6) drive, or produce a monoclonal protein; CLL more often lowers immunoglobulins over time.

  9. Recent intravenous immunoglobulin (IVIG) or plasma transfusion

    An infusion of IVIG raises IgG by hundreds of mg/dL for several weeks and is a common reason for an unexpectedly high result in someone being treated for immunodeficiency or autoimmune disease.

  10. Drug reactions and chronic allergic stimulation

    Some drug hypersensitivity syndromes and chronic antigen exposure produce a modest polyclonal rise, with IgG4 in particular rising after repeated exposure (allergen immunotherapy, chronic parasitic infection).

Symptoms that can go with it

  • Often none; a mildly high IgG is frequently found incidentally and reflects the underlying condition rather than the antibody level itself
  • Fatigue, fever, night sweats or weight loss with chronic infection, lymphoma or active autoimmune disease
  • Joint pain and swelling, rashes, dry eyes and dry mouth with connective tissue disease
  • Jaundice, itching, abdominal swelling or easy bruising with chronic liver disease
  • Bone pain (especially back or ribs), fatigue from anemia, excessive thirst and constipation from high calcium, or frequent infections with multiple myeloma
  • Swollen salivary or tear glands, abdominal pain, jaundice or kidney problems with IgG4-related disease
  • Headache, blurred vision, nosebleeds or confusion with hyperviscosity from a very high monoclonal protein (rare with IgG)

Low IgG

A low IgG (hypogammaglobulinemia) means you have less antibody than normal to neutralize bacteria, particularly the encapsulated organisms (pneumococcus, Hemophilus) that cause sinusitis, ear infections, bronchitis and pneumonia. The risk rises as the level falls: mild reductions (around 400 to 700 mg/dL) are often clinically silent or associated with slightly more frequent infections, while levels below 200 to 400 mg/dL carry a high risk of serious and recurrent infection. How low it is matters less than whether you are getting infections and whether you can make antibodies in response to vaccines.

The first question is whether the low IgG is primary (an inborn problem of antibody production) or secondary (caused by something else), because secondary causes are far more common in adults. Medications top the list: glucocorticoids, rituximab and other B-cell-depleting drugs, mycophenolate, some antiepileptics (phenytoin, carbamazepine) and chemotherapy. Protein loss through the kidneys (nephrotic syndrome) or gut (protein-losing enteropathy) lowers IgG with albumin. Blood cancers, particularly chronic lymphocytic leukemia and multiple myeloma, suppress normal immunoglobulin production; in myeloma the non-involved immunoglobulins are low while one M-protein is high.

Common variable immunodeficiency (CVID), the commonest symptomatic primary antibody deficiency, is diagnosed when IgG is markedly reduced (typically below about 400 to 450 mg/dL, or more than two standard deviations below the age mean) together with a low IgA or IgM, a poor antibody response to vaccines, and no secondary cause, in someone over 4 years old. It affects about 1 in 25,000 people, is usually diagnosed between 20 and 40, and is treated with immunoglobulin replacement, which cuts serious infections substantially. Transient hypogammaglobulinemia of infancy, a prolonged version of the normal dip at 3 to 6 months, resolves on its own by age 2 to 4.

Common causes

  1. Medications

    Long-term glucocorticoids (prednisone) lower IgG by 10 to 30 percent; rituximab and other anti-CD20 drugs can produce profound, sometimes lasting, hypogammaglobulinemia; mycophenolate, azathioprine, cyclophosphamide, phenytoin, carbamazepine, lamotrigine, sulfasalazine, CAR-T therapy and chemotherapy all reduce production.

  2. Common variable immunodeficiency (CVID)

    Markedly low IgG with low IgA and/or IgM and poor vaccine responses, presenting with recurrent sinopulmonary infections, often with autoimmune cytopenias, lymph node enlargement, granulomas or chronic diarrhea. Diagnosed at any age, most often 20 to 40.

  3. Other primary immunodeficiencies

    X-linked agammaglobulinemia (very low or absent IgG, IgA and IgM in boys from about 6 months), hyper-IgM syndromes (low IgG and IgA with normal or high IgM), and specific antibody deficiency with normal total IgG but failed vaccine responses.

  4. Multiple myeloma and other plasma-cell disorders

    The malignant clone suppresses normal plasma cells, so the uninvolved immunoglobulins fall; in light-chain myeloma all intact immunoglobulins including IgG can be low.

  5. Chronic lymphocytic leukemia and lymphoma

    Hypogammaglobulinemia develops in 25 to 70 percent of people with CLL over the course of the disease and is a major cause of their infections; non-Hodgkin lymphoma and its treatment can do the same.

  6. Protein loss: nephrotic syndrome and protein-losing enteropathy

    Heavy urinary protein loss or leakage from the gut (celiac disease, Crohn's disease, intestinal lymphangiectasia, severe heart failure) lowers IgG together with albumin; IgM, being larger, is lost less.

  7. Severe malnutrition, burns and critical illness

    Protein-energy malnutrition, extensive burns (loss through the wound) and sepsis all lower IgG; levels recover with nutrition and healing.

  8. Transient hypogammaglobulinemia of infancy

    An exaggerated and prolonged version of the normal 3-to-6-month dip, with low IgG but intact vaccine responses; resolves by age 2 to 4 and needs only watchful follow-up.

  9. Thymoma and some rare syndromes

    Good syndrome (thymoma with immunodeficiency) presents in adults over 40 with low or absent B cells and low IgG; other rare genetic syndromes also present as hypogammaglobulinemia.

Symptoms that can go with it

  • Recurrent or unusually severe bacterial infections: two or more sinus infections or pneumonias a year, repeated ear infections, or infections needing intravenous antibiotics
  • Chronic cough with sputum and recurring chest infections leading to bronchiectasis
  • Persistent diarrhea, bloating or weight loss, sometimes from Giardia or other gut infections
  • Infections that respond slowly to antibiotics or return as soon as they are stopped
  • Unexplained anemia, low platelets, enlarged lymph nodes or spleen (common in CVID)
  • Poor growth or failure to thrive in infants and children with inherited deficiency
  • Often no symptoms at all when the reduction is mild and caused by a medication

Read it alongside

  • IgA and IgM — the pattern across all three immunoglobulins separates global deficiency, selective deficiency and a monoclonal protein that suppresses the others.
  • Serum protein electrophoresis (SPEP) with immunofixation — the test that tells a polyclonal rise (broad band) from a monoclonal spike, and types the M-protein.
  • Serum free light chains — abnormal kappa/lambda ratio supports a plasma-cell disorder and is part of the myeloma and MGUS work-up.
  • Total protein, albumin and globulin — a high globulin gap (total protein minus albumin above about 4 g/dL) is often the first clue to a high immunoglobulin.
  • Complete blood count — anemia with high IgG raises concern for myeloma; low lymphocytes or neutrophils change the interpretation of recurrent infections.
  • Vaccine antibody titers (tetanus, pneumococcal) — a normal total IgG with absent responses to vaccines is specific antibody deficiency; poor responses are part of the CVID definition.
  • IgG subclasses — ordered when total IgG is normal but infections persist, or when IgG4-related disease is suspected.
  • Creatinine, calcium and urine protein — kidney impairment and high calcium with a monoclonal IgG point to myeloma; heavy urinary protein explains a low IgG.

What usually happens next

  1. A mildly abnormal IgG with no symptoms is usually repeated in 4 to 8 weeks together with IgA, IgM and protein electrophoresis before anything is concluded.
  2. For a high IgG: expect protein electrophoresis with immunofixation and free light chains to settle polyclonal versus monoclonal; a polyclonal rise is then traced to its cause (liver tests, HIV and hepatitis serology, autoimmune screen, chest imaging), while a monoclonal protein is staged with a blood count, calcium, creatinine and, depending on size, a marrow biopsy and skeletal imaging.
  3. For a low IgG: expect a review of every medication, a check for protein loss (urine protein, albumin), a blood count and electrophoresis to exclude a blood cancer, and vaccine antibody titers before and 4 weeks after a pneumococcal or tetanus booster to test whether you can make antibody.
  4. If you have had two or more serious infections in a year, or bronchiectasis, with a low IgG, ask for referral to an immunologist; immunoglobulin replacement (intravenous or subcutaneous) is standard for CVID and for secondary deficiency with recurrent infections.
  5. MGUS is followed with electrophoresis and blood tests every 6 to 12 months depending on risk; most people never progress, but the schedule should not lapse.
  6. Tell any new clinician if you have a low IgG: live vaccines may be unsuitable, and infections may need earlier and longer antibiotic treatment.

Diet, lifestyle and natural levers with evidence

What can move IgG once the cause is known. Nothing here replaces finding the cause.

Adequate protein and energy intake

Moderate evidence

Severe protein-energy malnutrition lowers IgG production and antibody responses, and refeeding restores them: in studies of malnourished children, immunoglobulin levels and vaccine responses normalized with nutritional rehabilitation over weeks. For adults this matters after bariatric surgery, with eating disorders, in advanced illness and in frailty; an intake of about 1 to 1.2 g of protein per kilogram a day is the usual target in older adults. In a well-nourished person, extra protein does not raise IgG further.

Vitamin D, if deficient

Moderate evidence

Vitamin D does not change the total IgG level, but a meta-analysis of 25 randomised trials (about 11,000 participants) found that daily or weekly vitamin D supplementation reduced acute respiratory infections by 12 percent overall and by about 70 percent in people starting below 10 ng/mL (25 nmol/L). For someone with a low IgG and recurrent chest infections, correcting a deficiency is a low-cost way of lowering infection risk; it is not a substitute for immunoglobulin replacement when that is indicated.

Keep to doses under 4,000 IU a day unless a clinician is monitoring levels; bolus doses of 100,000 IU or more did not reduce infections in the trials.

Zinc, if intake is low

Preliminary evidence

Zinc deficiency impairs B-cell and T-cell function and antibody production, and trials of zinc supplementation (around 20 to 45 mg a day) in deficient older adults and in children in low-income settings have improved some antibody responses and reduced infection rates; a Cochrane review found zinc reduced pneumonia incidence in children. There is no evidence it raises IgG in people who are zinc-replete, and it does not treat immunodeficiency.

More than 40 mg a day long term causes copper deficiency and anemia; high-dose zinc also interferes with some antibiotics.

Know what moves the test: medications, infusions and timing

Strong evidence

No supplement or diet raises a low IgG caused by a medication or an inherited deficiency, and none lowers a high IgG caused by chronic disease; the level follows the cause. Before interpreting a result, note any prednisone or other steroid, rituximab, antiepileptic, immunosuppressant or chemotherapy, any IVIG infusion in the previous 6 weeks (which raises IgG for about a month), a recent infection or vaccination (which can raise it slightly for weeks), and pregnancy (which lowers it modestly). Where a drug is the cause and can be adjusted, IgG recovers over months because its half-life is three weeks.

When to see a clinician promptly

  • A low IgG with a fever, a productive cough and breathlessness, severe sinus pain or ear pain, or any infection that is getting worse despite antibiotics; antibody-deficient people can deteriorate quickly.
  • A low IgG with fever and confusion, a stiff neck, a fast heart rate or low blood pressure: possible sepsis or meningitis, needs emergency care.
  • A high IgG with bone pain, unexplained anemia, excessive thirst, constipation, confusion or reduced urine output, which can indicate multiple myeloma with high calcium or kidney failure.
  • Headache, blurred vision, nosebleeds, bleeding gums or drowsiness with a very high immunoglobulin level: hyperviscosity syndrome needs same-day assessment.
  • Two or more pneumonias or four or more sinus or ear infections in a year, or bronchiectasis on a scan, with a low IgG: ask for immunology referral.
  • Any low IgG in a child with poor growth, persistent diarrhea or repeated infections, which needs evaluation for primary immunodeficiency.

Frequently asked questions

What is a normal IgG level?

For adults, about 700 to 1,600 mg/dL (7 to 16 g/L), with the exact range varying by lab. Children have lower, age-specific ranges: newborns carry their mother's IgG, levels fall to a low point at 3 to 6 months, then rise through childhood to reach adult values by the mid-teens. A value just outside the range in someone who feels well is usually repeated rather than acted on.

What does a high IgG mean?

Usually that the immune system has been stimulated for a long time by a chronic infection (such as HIV or hepatitis C), an autoimmune disease (lupus, rheumatoid arthritis, Sjögren's, autoimmune hepatitis), chronic liver disease or sarcoidosis. This is a polyclonal rise. Less often, a single plasma-cell clone is producing a monoclonal IgG, as in MGUS (3 percent of people over 50) or multiple myeloma. Serum protein electrophoresis is the test that tells the two apart, which is why it is almost always ordered next.

What does a low IgG mean?

That your body is making or keeping less antibody than normal, which raises the risk of bacterial infections of the sinuses, ears and lungs. In adults the usual causes are medications (steroids, rituximab, antiepileptics, immunosuppressants), protein loss through the kidneys or gut, and blood cancers such as CLL or myeloma. If none of these applies and IgA or IgM is also low with poor vaccine responses, the diagnosis may be common variable immunodeficiency, which is treated with immunoglobulin replacement.

What is the difference between IgG and IgM?

IgM is the first antibody made in a new infection, appearing within one to two weeks and fading over weeks to months; IgG follows a few weeks later and persists for years or life. On an infection test, a positive IgM suggests a recent or current infection, a positive IgG with negative IgM suggests past infection or vaccination, and both positive suggests a recent infection in the transition phase. IgM tests give more false positives, so a lone positive IgM is often confirmed with a repeat or a different method. On a total immunoglobulin panel, the two are measured as overall amounts rather than against any particular germ.

Does a high IgG mean I have cancer?

Rarely. Most high IgG results are polyclonal responses to infection, autoimmune or liver disease. A monoclonal IgG is found in about 3 percent of people over 50, but in the great majority it is MGUS, a premalignant condition that progresses to myeloma at only about 1 percent per year. Myeloma is suspected when the M-protein is 3 g/dL or more or there is anemia, kidney impairment, high calcium or bone pain, and is confirmed with free light chains, a marrow biopsy and imaging.

What are IgG subclasses and when are they tested?

IgG is made of four subclasses: IgG1 (60 to 70 percent), IgG2 (20 to 30 percent), IgG3 (5 to 8 percent) and IgG4 (under 5 percent). Subclasses are tested when someone has recurrent infections but a normal total IgG (an isolated IgG2 deficiency, for example, impairs responses to pneumococcus), and when IgG4-related disease is suspected, where an IgG4 above about 135 mg/dL supports the diagnosis. An isolated low subclass without infections or poor vaccine responses is usually of no consequence.

Can I raise a low IgG naturally?

Not meaningfully. IgG is made by plasma cells, and if they are suppressed by a medication, lost to a blood cancer or absent because of an inherited defect, no food or supplement restores it. What helps is correcting malnutrition if present, treating vitamin D or zinc deficiency to lower infection risk, reviewing whether a causative drug can be changed, and, when infections are recurrent, immunoglobulin replacement, which reliably raises IgG and cuts serious infections. Staying up to date with inactivated vaccines is also important, though responses may be reduced.

Do I need to fast for an IgG blood test?

No. Immunoglobulin levels are not affected by food. Tell the lab or clinician if you have had an IVIG infusion in the past 6 weeks, a recent infection or vaccination, or if you take steroids, rituximab or other immunosuppressants, since all of these shift the result. If a protein electrophoresis is being done on the same sample, a 24-hour urine collection for protein may be requested as well.

References

  1. Immunoglobulins blood test. MedlinePlus, US National Library of Medicine (2023)View source
  2. Common variable immunodeficiency (CVID). Merck Manual Professional Version (2024)
  3. Monoclonal gammopathy of undetermined significance (MGUS). Merck Manual Professional Version (2024)
  4. Bonilla FA, Khan DA, Ballas ZK, et al.. Practice parameter for the diagnosis and management of primary immunodeficiency. Journal of Allergy and Clinical Immunology (2015)
  5. Kyle RA, Therneau TM, Rajkumar SV, et al.. Prevalence of monoclonal gammopathy of undetermined significance. New England Journal of Medicine (2006)
  6. Rajkumar SV, Dimopoulos MA, Palumbo A, et al.. International Myeloma Working Group updated criteria for the diagnosis of multiple myeloma. Lancet Oncology (2014)
  7. Dispenzieri A, Gertz MA, Therneau TM, Kyle RA. Retrospective cohort study of 148 patients with polyclonal gammopathy. Mayo Clinic Proceedings (2001)
  8. Umehara H, Okazaki K, Masaki Y, et al.. Comprehensive diagnostic criteria for IgG4-related disease (IgG4-RD), 2011. Modern Rheumatology (2012)
  9. Perez EE, Orange JS, Bonilla F, et al.. Update on the use of immunoglobulin in human disease: a review of evidence. Journal of Allergy and Clinical Immunology (2017)
  10. Martineau AR, Jolliffe DA, Hooper RL, et al.. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ (2017)
  11. Gonzalez-Quintela A, Alende R, Gude F, et al.. Serum levels of immunoglobulins (IgG, IgA, IgM) in a general adult population and their relationship with alcohol consumption, smoking and common metabolic abnormalities. Clinical and Experimental Immunology (2008)
  12. Patel SY, Carbone J, Jolles S. Secondary immunodeficiency: diagnosis and management. Frontiers in Immunology (2019)

Related markers

Related conditions

Evidence guides

Worried about your number?

Ask AskMN what your IgG result could mean in the context of your other results, symptoms and medications. Free, unlimited, no account needed.

Ask about my IgG

This page is educational and is not medical advice or a diagnosis. Lab results have to be interpreted together with your history, symptoms and other results by a clinician who knows you. Do not start or stop a supplement to change a lab value before the cause is known.