Lab result explainedMetabolic panelLast updated November 10, 2026

Fructosamine test: normal range, what high means, and how it converts to A1C

Fructosamine · Ordered on its own, usually alongside or instead of A1C · reported in umol/L (micromoles per liter)

Fructosamine is a blood test that measures how much sugar has become attached to the proteins in your blood, mainly albumin, and it reflects your average blood glucose over the previous two to three weeks. A normal result is roughly 200 to 285 umol/L in people without diabetes (ranges vary by lab; 190 to 270 and 205 to 285 are common). It does the same job as the A1C test but over a much shorter window, because albumin lives in the blood for about 20 days whereas red blood cells, which A1C depends on, last about 120.

That shorter window is the reason the test exists. Fructosamine is used when A1C cannot be trusted: in sickle cell trait and disease, thalassemia and other hemoglobin variants, hemolytic anemia, recent blood transfusion or heavy blood loss, iron deficiency, advanced kidney disease and pregnancy, all of which change red cell survival and make A1C read falsely high or low. It is also useful when treatment has just changed and a 3-month A1C is too slow to show the effect, in gestational diabetes, and when a person's A1C and home glucose readings do not match.

The conversion to A1C is approximate. A commonly used equation is A1C (%) = 0.017 x fructosamine (umol/L) + 1.61, which makes 250 umol/L about 5.9 percent, 300 about 6.7, 350 about 7.6 and 400 about 8.4. Each 1 percentage-point change in A1C corresponds to roughly 50 to 60 umol/L of fructosamine. The two tests measure different proteins over different time frames, so a gap between them is expected and sometimes informative rather than a mistake.

Fructosamine at a glance

What it is: glucose bound to blood proteins (mostly albumin); an average of blood sugar over the past 2 to 3 weeks.
Normal (no diabetes): about 200-285 umol/L; labs differ (190-270 or 205-285 are also used). Well-controlled diabetes often runs 285-320.
Rough A1C equivalents: 250 = 5.9%, 300 = 6.7%, 350 = 7.6%, 400 = 8.4%, 450 = 9.3% (A1C = 0.017 x fructosamine + 1.61).
High: blood sugar has been high over the past few weeks; above about 320-350 usually means diabetes is not well controlled.
Falsely low: low albumin (liver disease, kidney protein loss, malnutrition), overactive thyroid, high-dose vitamin C. Falsely high: high protein or IgA levels, underactive thyroid.
Next step: used instead of A1C when red cells are abnormal or control has recently changed; repeat every 2 to 4 weeks while adjusting treatment.

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What Fructosamine measures

Glucose in the blood reacts spontaneously with the amino groups of proteins, forming a stable sugar-protein compound called a ketoamine; the collective name for these glycated serum proteins is fructosamine. Albumin makes up about 60 percent of blood protein and most of the measured fructosamine, which is why the test is sometimes called a proxy for glycated albumin. The higher the average glucose, the more protein is glycated, and because albumin turns over every 2 to 3 weeks the test integrates glucose over that period, weighted toward the most recent week.

The lab measures fructosamine with a color reaction (nitroblue tetrazolium) on a serum sample; no fasting is needed. Results are reported in umol/L. A related, more specific test, glycated albumin, is reported as a percentage of total albumin and is more widely used in Japan and in some US centers; it behaves the same way but is less affected by total protein. Neither test is affected by red cell lifespan, hemoglobin variants, transfusion or iron deficiency, the main things that distort A1C.

The weakness of fructosamine is its dependence on protein. When albumin is low (under about 3.0 g/dL) because of liver disease, nephrotic syndrome, protein-losing gut disease or malnutrition, or when protein turnover is fast (hyperthyroidism, high-dose steroids), fructosamine reads low regardless of glucose. High immunoglobulin levels (myeloma, IgA nephropathy), hypothyroidism and very high triglycerides or bilirubin can push it the other way, and large doses of vitamin C interfere with the assay. Some laboratories report an albumin-corrected value for this reason.

Normal range for Fructosamine

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

Group	Typical range (umol/L (micromoles per liter))	Notes
No diabetes, typical reference range	About 200-285 umol/L	Labs differ: 190-270, 205-285 and 170-285 umol/L are all in use. Use the range on your report.
Well-controlled diabetes	About 285-320 umol/L	Roughly equivalent to an A1C of 6.5 to 7.0 percent, the usual target range for most adults with diabetes.
Moderately raised	320-380 umol/L	Roughly A1C 7.0 to 8.0 percent; treatment review usually warranted.
Markedly raised	Above 380 umol/L	Roughly A1C above 8 percent; sustained average glucose over about 180 mg/dL in the past 2 to 3 weeks.
A1C conversion (approximate)	250 = 5.9%, 300 = 6.7%, 350 = 7.6%, 400 = 8.4%, 450 = 9.3%, 500 = 10.1%	From A1C = 0.017 x fructosamine + 1.61. Other published equations give values within about 0.3 percentage points; treat as a guide, not an exact conversion.
Pregnancy	Lower than non-pregnant, roughly 170-240 umol/L	Albumin falls in pregnancy. Some centers use fructosamine to monitor gestational diabetes between glucose checks.
Low albumin (under 3.0 g/dL)	Falsely low	Cirrhosis, nephrotic syndrome, protein-losing enteropathy, severe malnutrition. Glycated albumin (percentage) or continuous glucose monitoring is preferred.
Children	Slightly lower than adults	Age-specific ranges are used; interpret with a pediatric reference.

High fructosamine

A high fructosamine means your average blood glucose has been above normal for the past two to three weeks. In someone with known diabetes, a value of 320 to 350 umol/L corresponds to an A1C of roughly 7 to 7.5 percent and signals that control has slipped; 400 or above (A1C about 8.4 percent and up) means average glucose has been running around 190 mg/dL or higher and treatment needs attention. Because the window is short, a high fructosamine after a recent illness, course of steroids or lapse in medication reflects those weeks specifically, which is both its strength and its limitation.

In someone not known to have diabetes, a raised fructosamine suggests diabetes or prediabetes but is not a recognized diagnostic test on its own; the American Diabetes Association diagnoses diabetes with fasting glucose, 2-hour glucose tolerance test or A1C. A high fructosamine would prompt one of those. In large population studies (ARIC), a fructosamine above about 270 to 285 umol/L predicted future diabetes, kidney disease and retinopathy about as well as A1C did, so the number is meaningful even if it is not formally diagnostic.

A fructosamine that is high while A1C is normal usually means glucose has risen recently (new diabetes, a steroid course, pregnancy) and the A1C has not caught up, or that the A1C is falsely low because red cells are being turned over quickly (hemolysis, bleeding, recent transfusion, treatment of iron deficiency). The reverse, a normal fructosamine with a high A1C, points to a falsely high A1C (iron deficiency, kidney failure, some hemoglobin variants) or to recent improvement in control.

Common causes

Diabetes with high recent glucose
The usual cause. Missed medication, dietary change, weight gain, reduced activity or progression of the diabetes raise the 2 to 3 week average; fructosamine moves within 1 to 2 weeks of the change, well before A1C.
New or undiagnosed diabetes or prediabetes
A fructosamine above the reference range in someone never tested is a prompt for a fasting glucose, A1C or glucose tolerance test.
Steroid treatment and acute illness
Prednisone, dexamethasone and other glucocorticoids raise glucose within days; a pneumonia, surgery or heart attack does the same through stress hormones. A short course shows up on fructosamine but barely moves A1C.
Gestational diabetes
Pregnancy hormones cause insulin resistance from mid-pregnancy; fructosamine is sometimes used to track control because A1C is unreliable in pregnancy. Pregnancy ranges are lower, so the usual cut-offs do not apply.
High blood protein or immunoglobulins
Multiple myeloma, IgA nephropathy, chronic inflammation with high globulins and dehydration raise total protein and therefore fructosamine independent of glucose.
Hypothyroidism
Slow protein turnover prolongs albumin's exposure to glucose, pushing fructosamine up by 10 to 20 percent for the same average glucose.
Severe hypertriglyceridemia, high bilirubin or hemolysed sample
Lipemic, icteric or hemolysed samples interfere with the color assay and can read high; the lab usually flags this.
Other diabetes types and conditions
Pancreatic diabetes after pancreatitis or surgery, Cushing's syndrome, acromegaly and drugs such as antipsychotics or tacrolimus raise glucose and therefore fructosamine.

Symptoms that can go with it

Often none when the rise is modest
Thirst, dry mouth and frequent urination, including at night
Tiredness, blurred vision and irritability
Weight loss despite eating normally, if insulin deficiency is developing
Recurrent thrush, urinary infections or slow-healing cuts
Numbness or tingling in the feet with longer-standing high glucose
Nausea, vomiting, abdominal pain or rapid breathing with very high glucose, which can mean ketoacidosis

Low fructosamine

A low fructosamine, below the lab's reference range, is uncommon and rarely means low blood sugar. In someone with diabetes it can reflect very tight or improving control over the past few weeks, and if it comes with episodes of hypoglycemia the treatment may be too strong. More often, though, a low value is a protein problem rather than a glucose problem: the test depends on albumin, so anything that lowers albumin below about 3.0 g/dL, or speeds up its turnover, lowers fructosamine regardless of glucose.

Low albumin from cirrhosis, nephrotic syndrome, protein-losing bowel disease, severe malnutrition or critical illness, and fast protein turnover from hyperthyroidism or high-dose steroids, are the usual explanations. In these situations fructosamine underestimates average glucose and should not be used to judge diabetes control; glycated albumin reported as a percentage, frequent glucose checks or a continuous glucose monitor are the alternatives. Very large doses of vitamin C (grams a day) also interfere with the assay and lower the reading.

Common causes

Low albumin (hypoalbuminemia)
Cirrhosis, nephrotic syndrome, protein-losing enteropathy, severe burns, malnutrition and critical illness reduce the protein available to glycate; fructosamine falls by roughly 10 percent for each 0.5 g/dL drop in albumin.
Hyperthyroidism
Fast protein turnover shortens albumin's time in circulation, lowering fructosamine by 10 to 20 percent for the same average glucose. Values rise again when the thyroid is treated.
Tight or improving diabetes control
After starting or intensifying treatment, fructosamine falls within 2 to 3 weeks; a low value with frequent lows suggests over-treatment.
High-dose vitamin C and some drugs
Ascorbic acid at gram doses reduces the color reaction used in the assay; high-dose aspirin and some antioxidants have been reported to do the same.
Pregnancy
Plasma volume expands and albumin falls, so fructosamine is normally 10 to 20 percent lower than outside pregnancy; pregnancy-specific ranges apply.
Recent plasma exchange or heavy protein loss
Replacing or losing plasma proteins resets the glycated pool, giving a transiently low result that does not reflect glucose.

Symptoms that can go with it

None from the fructosamine itself
Sweating, shaking, hunger or confusion if the low value reflects over-treated diabetes with hypoglycemia
Swelling of the ankles or abdomen, foamy urine or jaundice if albumin is low from kidney or liver disease
Weight loss, heat intolerance, tremor or a fast heartbeat if the cause is an overactive thyroid
Muscle wasting and fatigue with malnutrition

Read it alongside

A1C — the 3-month average; fructosamine and A1C that disagree point to a recent change in control or a reason A1C is unreliable.
Albumin and total protein — a low albumin (under 3.0 g/dL) makes fructosamine falsely low; some labs correct for it.
Fasting glucose or home glucose readings — fructosamine should be consistent with the pattern of recent readings; if not, one of them is misleading.
Hemoglobin, MCV, reticulocyte count and hemoglobin electrophoresis — explain why A1C was unreliable (hemolysis, iron deficiency, sickle or thalassemia trait) when fructosamine was ordered instead.
TSH — hypothyroidism raises and hyperthyroidism lowers fructosamine independently of glucose.
Creatinine, eGFR and urine protein — advanced kidney disease distorts A1C, and nephrotic-range protein loss lowers albumin and fructosamine.
Glycated albumin — a related test reported as a percentage that is less affected by total protein; preferred where available in liver disease and nephrotic syndrome.

What usually happens next

If fructosamine is high and you do not have a diabetes diagnosis, expect a fasting glucose, A1C or oral glucose tolerance test, since those are the recognized diagnostic tests.
If you have diabetes and the result is above your target, review what changed in the past 3 weeks (illness, steroids, missed doses, diet, activity) with your clinician and expect a treatment adjustment; recheck in 2 to 4 weeks.
If fructosamine and A1C disagree, ask which one is likely to be wrong for you: check albumin, a blood count, iron studies, kidney function and whether you have a hemoglobin variant.
If albumin is low or you have liver or nephrotic kidney disease, ask whether glycated albumin or a continuous glucose monitor would be a better way to track control.
In pregnancy, fructosamine is read against pregnancy-specific ranges and used alongside, not instead of, home glucose monitoring.
Stop high-dose vitamin C supplements for a few days before a repeat test if you take them, and tell the lab about thyroid disease or any recent transfusion or plasma exchange.

Diet, lifestyle and natural levers with evidence

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

Weight loss of 5 to 15 percent in type 2 diabetes

Strong evidence

Fructosamine falls as average glucose falls, and weight loss is the most powerful lever in type 2 diabetes. In the DiRECT trial, a structured low-calorie program producing an average 10 kg loss led to diabetes remission (A1C under 6.5 percent off medication) in 46 percent of participants at one year and 36 percent at two years. Because fructosamine responds within 2 to 3 weeks, it shows the effect of a dietary change long before A1C does.

Aerobic and resistance exercise

Strong evidence

Meta-analyses of structured exercise trials in type 2 diabetes show A1C reductions of about 0.6 to 0.7 percentage points, equivalent to a fall of roughly 30 to 40 umol/L in fructosamine, with combined aerobic and resistance training giving the largest effect. Each session lowers glucose for 24 to 48 hours, so most days of the week is the dose that moves a 2 to 3 week average.

Viscous fiber (psyllium, oats, barley beta-glucan, legumes)

Moderate evidence

A meta-analysis of 28 randomised trials found that adding about 13 g a day of viscous fiber lowered A1C by 0.58 percentage points and fasting glucose by about 15 mg/dL in people with type 2 diabetes over a median of 8 weeks, a time frame fructosamine captures well. The fiber slows carbohydrate absorption and blunts post-meal glucose peaks.

Increase gradually with plenty of water to limit bloating; take psyllium 1 to 2 hours apart from medications, as it can reduce their absorption.

Mediterranean or low-glycemic-index eating pattern

Moderate evidence

Network meta-analyses of dietary trials in type 2 diabetes rank Mediterranean, low-glycemic-index and low-carbohydrate patterns highest for A1C, with reductions of about 0.3 to 0.5 percentage points versus control diets (roughly 15 to 30 umol/L of fructosamine). The common thread is replacing refined grains, potatoes and sugary drinks with vegetables, legumes, whole grains, nuts and olive oil.

Berberine

Moderate evidence

A meta-analysis of 27 randomised trials in type 2 diabetes found berberine, 0.9 to 1.5 g a day for 2 to 3 months, lowered A1C by about 0.7 percentage points and fasting glucose by about 15 mg/dL, similar to metformin in direct comparisons. Trials are small and mostly from one country, so the evidence is moderate.

Adds to the effect of diabetes drugs, so monitor for low glucose; inhibits enzymes that clear many medications; causes constipation in some; avoid in pregnancy, breastfeeding and newborns.

Cinnamon

Preliminary evidence

Meta-analyses of small trials of cinnamon (1 to 6 g a day) in type 2 diabetes report fasting glucose reductions of about 10 to 25 mg/dL but inconsistent and mostly non-significant effects on A1C, so any effect on a 2 to 3 week average is likely to be small.

Cassia cinnamon contains coumarin, which can harm the liver at several grams a day; Ceylon cinnamon contains far less.

When to see a clinician promptly

High glucose with nausea, vomiting, abdominal pain, deep rapid breathing, drowsiness or confusion: possible diabetic ketoacidosis or hyperosmolar state, call emergency services.
A fructosamine above about 380 umol/L (A1C roughly 8 percent or more), or any value well above your previous results, for a prompt treatment review.
A high fructosamine in someone without a diabetes diagnosis, so a formal diagnostic test can be done.
Repeated episodes of hypoglycemia (sweating, shaking, confusion, glucose under 70 mg/dL) with a fructosamine that has fallen sharply, which can mean treatment is now too strong.
Fructosamine and A1C that point in opposite directions, so the reason (anemia, hemoglobin variant, kidney or liver disease, thyroid disease) can be found before either number guides treatment.
In pregnancy, any fructosamine above the pregnancy range or glucose readings above targets, since control affects the baby within weeks.

Frequently asked questions

What is a normal fructosamine level?

In people without diabetes, roughly 200 to 285 umol/L, though laboratories use somewhat different ranges (190 to 270 and 205 to 285 are common) and your report's range is the one to use. People with well-controlled diabetes usually run about 285 to 320 umol/L, equivalent to an A1C of 6.5 to 7 percent. Values are 10 to 20 percent lower in pregnancy and in anyone with a low albumin.

How do I convert fructosamine to A1C?

A widely used equation is A1C (%) = 0.017 x fructosamine (umol/L) + 1.61. So 250 umol/L is about 5.9 percent, 300 about 6.7, 350 about 7.6, 400 about 8.4 and 450 about 9.3. A quicker rule of thumb is that each 50 to 60 umol/L equals about 1 percentage point of A1C. The conversion is approximate: the two tests cover different time periods and different proteins, and several published equations differ from each other by a few tenths of a percent.

What is the difference between fructosamine and A1C?

Both measure glucose stuck to a protein, but A1C uses hemoglobin inside red cells, which live about 120 days, so it averages the past 2 to 3 months; fructosamine uses albumin and other serum proteins, which turn over in 2 to 3 weeks, so it averages the past few weeks. A1C is the standard for diagnosis and long-term monitoring and predicts complications best; fructosamine is used when red cells are abnormal (sickle cell, thalassemia, hemolysis, transfusion, iron deficiency, kidney failure, pregnancy) or when a faster readout is needed.

Is a fructosamine of 300 high?

A fructosamine of 300 umol/L is above the non-diabetic range in most labs and corresponds to an A1C of about 6.7 percent, which is at the upper edge of the usual target for someone with diabetes and in the diabetic range for someone without a diagnosis. In a person with diabetes it suggests reasonable but not tight control over the past three weeks; in someone untested it should lead to a fasting glucose or A1C to confirm whether diabetes is present.

Why would my doctor order fructosamine instead of A1C?

Usually because something makes your A1C unreliable: sickle cell trait or disease, thalassemia or another hemoglobin variant, hemolytic anemia, a recent transfusion or major bleed, iron deficiency or its treatment, dialysis or advanced kidney disease, pregnancy, or treatment with erythropoietin. The other reasons are wanting to see the effect of a treatment change within weeks rather than months, and a mismatch between your A1C and your glucose meter readings.

Can fructosamine be falsely high or low?

Yes, mainly because it depends on blood protein rather than glucose alone. It reads falsely low when albumin is low (cirrhosis, nephrotic syndrome, protein-losing bowel disease, malnutrition), when protein turnover is fast (hyperthyroidism, high-dose steroids) and with large doses of vitamin C. It reads falsely high with high immunoglobulins (myeloma, chronic inflammation), hypothyroidism and in lipemic or hemolysed samples. A low albumin is the commonest problem; some labs correct for it, and glycated albumin as a percentage avoids it.

Do I need to fast for a fructosamine test?

No. Fructosamine reflects the average of the past 2 to 3 weeks and is not changed by what you ate that morning, so it can be drawn at any time, and it is often added to a sample taken for other reasons. Tell the lab if you take high-dose vitamin C, have thyroid disease, kidney or liver disease, or are pregnant, since these affect interpretation.

How quickly does fructosamine change?

Within one to two weeks of a real change in average glucose, and it fully reflects a new level after about 3 weeks. That makes it useful for checking whether a new medication, insulin dose or diet is working: a fall of 30 to 40 umol/L over 3 to 4 weeks corresponds to roughly a 0.6 percentage-point drop in A1C that would otherwise take 3 months to confirm. For the same reason a single bad fortnight (illness, steroids, holidays) shows up clearly and then washes out.

References

Armbruster DA. Fructosamine: structure, analysis, and clinical usefulness. Clinical Chemistry (1987)View source
Selvin E, Rawlings AM, Grams M, et al.. Fructosamine and glycated albumin for risk stratification and prediction of incident diabetes and microvascular complications: a prospective cohort analysis of the Atherosclerosis Risk in Communities (ARIC) study. The Lancet Diabetes and Endocrinology (2014)View source
Danese E, Montagnana M, Nouvenne A, Lippi G. Advantages and pitfalls of fructosamine and glycated albumin in the diagnosis and treatment of diabetes. Journal of Diabetes Science and Technology (2015)View source
Parrinello CM, Selvin E. Beyond HbA1c and glucose: the role of nontraditional glycemic markers in diabetes diagnosis, prognosis, and management. Current Diabetes Reports (2014)
Radin MS. Pitfalls in hemoglobin A1c measurement: when results may be misleading. Journal of General Internal Medicine (2014)View source
American Diabetes Association Professional Practice Committee. Glycemic goals and hypoglycemia: Standards of Care in Diabetes - 2025. Diabetes Care (2025)
The A1C test and diabetes. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) (2018)View source
Hemoglobin A1C (HbA1c) test. MedlinePlus, US National Library of Medicine (2023)View source
Lean MEJ, Leslie WS, Barnes AC, et al.. Primary care-led weight management for remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial. The Lancet (2018)View source
Jovanovski E, Khayyat R, Zurbau A, et al.. Should viscous fiber supplements be considered in diabetes control? Results from a systematic review and meta-analysis of randomized controlled trials. Diabetes Care (2019)View source
Lan J, Zhao Y, Dong F, et al.. Meta-analysis of the effect and safety of berberine in the treatment of type 2 diabetes mellitus, hyperlipemia and hypertension. Journal of Ethnopharmacology (2015)
Diabetes mellitus (DM): diagnosis. Merck Manual Professional Version (2024)

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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.