Lab result explainedKidneyLast updated November 1, 2026

Creatinine blood test: what high and low creatinine levels mean

Creatinine · Comprehensive metabolic panel (CMP) / Basic metabolic panel (BMP) · reported in mg/dL (micromol/L outside the US; 1 mg/dL = 88.4 micromol/L)

Creatinine is a waste product that your muscles make at a steady rate and your kidneys filter out of the blood, which is why it is the most common blood test of kidney function. A typical adult range is about 0.74 to 1.35 mg/dL for men and 0.59 to 1.04 mg/dL for women, though every lab prints its own limits. The two most common reasons it reads high are reduced kidney filtration and simply having more muscle than average; the most common reason it reads low is having less muscle.

Because creatinine comes from muscle, the same number means different things in different bodies. A creatinine of 1.3 mg/dL may be normal for a muscular 25-year-old man and a sign of significantly reduced kidney function in a slight 80-year-old woman. That is why labs convert creatinine into an estimated glomerular filtration rate (eGFR), which adjusts for age and sex, and why the eGFR is the number to focus on.

Creatinine also moves for reasons that have nothing to do with the kidneys: a creatine supplement, a cooked-meat meal before the draw, dehydration, intense exercise and a handful of common medicines. This page walks through each, explains when a high creatinine is a real kidney signal, and sets out what can genuinely lower it.

Creatinine at a glance

  • What it is: a muscle waste product cleared by the kidneys; the standard blood test of kidney filtration.
  • Normal: about 0.74 to 1.35 mg/dL (men) and 0.59 to 1.04 mg/dL (women); ranges vary by lab, age and muscle mass.
  • High creatinine: reduced kidney filtration, dehydration, high muscle mass, creatine supplements, a cooked-meat meal, or drugs such as trimethoprim and NSAIDs.
  • Low creatinine: low muscle mass, pregnancy, liver disease, malnutrition or overhydration; rarely a problem on its own.
  • eGFR matters more: the same creatinine can be a normal or a worrying eGFR depending on age and sex.
  • Next step: repeat it well hydrated, off creatine and cooked meat, with a urine albumin test and eGFR trend.

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What Creatinine measures

Muscle stores energy as creatine phosphate. Each day about 1 to 2 percent of that creatine breaks down spontaneously into creatinine, which enters the blood and is removed almost entirely by the kidneys. Production is roughly constant from hour to hour and depends on how much muscle you have, so the blood level reflects a balance between muscle output and kidney clearance.

The kidneys handle creatinine mainly by filtering it at the glomerulus. A small share, around 10 to 15 percent, is actively secreted by the tubules, which is why some drugs that block that secretion nudge the level up without harming the kidney. Creatinine is not reabsorbed, which makes it a cleaner marker of filtration than BUN.

Most US labs measure creatinine with an enzymatic or a calibrated Jaffe method and report mg/dL. From that value, your age and sex, the lab calculates eGFR using the 2021 CKD-EPI equation, which no longer uses race. Some labs also offer cystatin C, a filtration marker independent of muscle, when creatinine may mislead.

Normal range for Creatinine

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

GroupTypical range (mg/dL (micromol/L outside the US; 1 mg/dL = 88.4 micromol/L))Notes
Adult men0.74–1.35 mg/dL
Adult women0.59–1.04 mg/dL
Older adults (70+)Often 0.6–1.2 mg/dLLower muscle mass; a value at the top of the range can mean a reduced eGFR.
Pregnancy0.4–0.8 mg/dLFiltration rises by 40 to 50 percent; a 'normal' 1.0 can be abnormal in pregnancy.
Children0.2–0.7 mg/dL depending on ageUse age-specific pediatric ranges.
Muscular adults and athletesMay run 1.3–1.5 mg/dL with normal kidneysConfirm with cystatin C if in doubt.

High creatinine

A high creatinine means either the kidneys are filtering less than expected, or more creatinine is being produced or retained for a non-kidney reason. The first question is always whether the eGFR is below 60 and whether this is new. A rise of 0.3 mg/dL or more within 48 hours, or a 50 percent rise within a week, meets the definition of acute kidney injury and needs prompt evaluation.

A creatinine that is stably a little high for years, with an eGFR in the 60s and no protein in the urine, is common in older adults and carries a much lower risk than a creatinine that is climbing. Trend matters more than any single value.

Before concluding the kidneys are the problem, clinicians rule out the usual confounders: dehydration, a creatine supplement, a large cooked-meat meal in the previous 12 hours, strenuous exercise, and medicines that raise creatinine without reducing filtration.

Common causes

  1. Chronic kidney disease

    Diabetes, high blood pressure, glomerulonephritis and polycystic kidney disease slowly reduce the number of working filters, so creatinine accumulates. The rise is gradual and usually accompanied by protein in the urine.

  2. Dehydration

    Low blood volume reduces blood flow through the glomeruli, so less creatinine is filtered. Creatinine can climb 0.2 to 0.5 mg/dL after a stomach bug or a hot day and settle again once rehydrated.

  3. High muscle mass

    More muscle means more creatine turning over. Bodybuilders and large, muscular people routinely run 1.3 to 1.5 mg/dL with perfectly normal kidneys; cystatin C stays normal.

  4. Creatine supplements

    Supplemental creatine is converted to creatinine at a steady rate. A typical 3 to 5 g daily dose raises creatinine by around 0.1 to 0.3 mg/dL, and a loading phase can raise it more, without any change in true filtration.

  5. Cooked-meat meal before the test

    Cooking converts the creatine in meat to creatinine, which is absorbed directly. Trials show a cooked-meat meal raises serum creatinine for several hours and can drop the calculated eGFR by 10 to 20 points.

  6. Medicines that block tubular secretion

    Trimethoprim (in Bactrim), cimetidine, fenofibrate and some HIV drugs such as dolutegravir and cobicistat stop the tubules secreting creatinine. The level rises by 0.2 to 0.3 mg/dL within days and returns to baseline when the drug stops.

  7. NSAIDs, ACE inhibitors, ARBs and SGLT2 inhibitors

    These change blood flow or pressure inside the glomerulus. A small, stable rise of up to 30 percent after starting an ACE inhibitor, ARB or SGLT2 inhibitor is expected and acceptable; NSAIDs plus dehydration can cause true acute kidney injury.

  8. Urinary obstruction

    An enlarged prostate, kidney stone or pelvic tumour blocks urine outflow and backs pressure up into the kidney, reducing filtration from both sides if the bladder outlet is blocked.

  9. Rhabdomyolysis and intense exercise

    Severe muscle breakdown releases creatinine and myoglobin; the myoglobin can also injure the kidney. A marathon or heavy lifting session can raise creatinine by 0.1 to 0.3 mg/dL for a day or two.

  10. Heart failure and liver cirrhosis

    Both reduce effective blood flow to the kidney. In cirrhosis, low muscle mass hides the problem, so a creatinine that looks normal may already represent a reduced eGFR.

Symptoms that can go with it

  • Often none until kidney function is substantially reduced
  • Swelling of the legs, ankles or around the eyes
  • Fatigue, poor concentration, nausea or loss of appetite
  • Passing less urine, foamy urine, or getting up at night to urinate
  • Itching, muscle cramps or a metallic taste in advanced disease
  • Rising blood pressure that is harder to control

Low creatinine

Low creatinine almost always means less muscle rather than better kidneys. Older adults, small-framed people, those who have lost weight or muscle through illness, and people with limb loss all run low. The kidneys cannot lower creatinine below what muscle produces, so a low value is not a sign of unusually good filtration.

The practical importance is that a low creatinine makes the eGFR read artificially high. Someone with sarcopenia can have a creatinine of 0.5 mg/dL, an eGFR above 90, and still have significantly reduced kidney function. When muscle mass is low, cystatin C gives a truer picture.

Low creatinine in pregnancy is normal and expected; a value that is normal for a non-pregnant adult can signal a kidney problem in pregnancy.

Common causes

  1. Low muscle mass

    Ageing, sarcopenia, long illness, immobility or small body size reduce the daily creatinine output. This is the most common cause by far.

  2. Pregnancy

    Blood volume and kidney filtration increase from early pregnancy, clearing creatinine faster; values of 0.4 to 0.6 mg/dL are typical.

  3. Malnutrition and eating disorders

    Low protein and calorie intake lead to muscle wasting and reduced creatine stores, both of which lower creatinine production.

  4. Liver disease

    The liver makes about half of the body's creatine. Cirrhosis reduces creatine synthesis and causes muscle loss, so creatinine runs low even when kidney function is impaired.

  5. Overhydration or large intravenous fluid volumes

    Excess water expands plasma volume and dilutes creatinine for a short time.

  6. Vegetarian or vegan diet

    Meat supplies preformed creatine and creatinine. People who eat no meat have modestly lower creatinine, by roughly 0.1 mg/dL on average, with normal kidneys.

  7. Muscular dystrophy and neuromuscular disease

    Progressive loss of muscle tissue lowers creatinine production; levels can fall well below the lab range.

Symptoms that can go with it

  • Usually none; low creatinine itself causes no symptoms
  • Loss of strength, thinner arms and legs, or falls (muscle loss)
  • Unintended weight loss or poor appetite (malnutrition)
  • Jaundice, abdominal swelling or easy bruising if liver disease is the cause

Read it alongside

  • eGFR — the creatinine adjusted for age and sex; below 60 for more than three months defines chronic kidney disease.
  • Cystatin C — a filtration marker independent of muscle mass; it settles the question when creatinine is high from muscle or low from frailty.
  • BUN and BUN/creatinine ratio — a ratio above 20 points to dehydration or bleeding rather than kidney damage.
  • Urine albumin-to-creatinine ratio (UACR) — albumin in the urine is kidney damage even when creatinine is normal, and it predicts progression.
  • Potassium and CO2 (bicarbonate) — high potassium or low bicarbonate with a high creatinine mark kidney disease that is affecting chemistry and needs faster action.
  • Hemoglobin — anemia often appears once eGFR falls below 45 and supports a chronic rather than acute process.
  • Creatine kinase (CK) — very high CK with a rising creatinine indicates rhabdomyolysis.

What usually happens next

  1. A mildly high creatinine with no symptoms is usually repeated within one to two weeks, fasting, well hydrated, off creatine and without a cooked-meat meal in the previous 12 hours.
  2. Your clinician will add a urine albumin-to-creatinine ratio and look at the eGFR trend from previous tests; a stable value for years is reassuring, a rising one is not.
  3. If muscle mass is unusually high or low, ask for cystatin C and an eGFR calculated from both markers (the CKD-EPI creatinine-cystatin equation).
  4. Medicines are reviewed: NSAIDs, trimethoprim, cimetidine, lithium, ACE inhibitors, ARBs, diuretics and SGLT2 inhibitors all deserve a mention.
  5. A kidney ultrasound is ordered when obstruction, polycystic kidneys or a difference between the two kidneys is suspected.
  6. An eGFR persistently below 60, a UACR above 30 mg/g, or a rapid rise in creatinine is the usual threshold for a nephrology referral.

Diet, lifestyle and natural levers with evidence

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

Hydration to correct a dry sample

Moderate evidence

Dehydration is the most common reversible cause of a raised creatinine, and rehydration typically normalises a prerenal rise within 24 to 48 hours. Beyond correcting dehydration, however, drinking extra water does not improve kidney function: the CKD WIT trial randomised 631 adults with CKD to about 1 litre more water daily for a year and found no difference in eGFR decline.

People with heart failure or advanced CKD may be on a fluid limit.

Skip cooked meat and creatine before the test

Moderate evidence

A single cooked-meat meal raised serum creatinine and lowered calculated eGFR for several hours in crossover studies of healthy volunteers and people with diabetic kidney disease, in some cases shifting a person's CKD stage. Creatine supplements add a steady 0.1 to 0.3 mg/dL. Fasting, and a 7 to 14 day creatine break, remove both artefacts.

Blood pressure and blood sugar control

Strong evidence

High blood pressure and diabetes cause most chronic kidney disease, and treating them is the intervention with the best evidence for slowing creatinine rise. Intensive blood pressure control in SPRINT and tight glucose control in large diabetes trials reduced albuminuria and slowed eGFR loss. Lifestyle (weight loss, sodium under 2 g a day, exercise) is part of that treatment, not a replacement for it.

DASH or Mediterranean-style eating

Moderate evidence

In the ARIC cohort of nearly 15,000 adults, those closest to a DASH pattern had a 45 percent lower risk of developing CKD over 23 years than those furthest from it. A meta-analysis of cohort studies in people with existing CKD linked healthy dietary patterns to lower mortality. Plant-forward diets also lower the dietary acid load that stresses damaged kidneys.

Avoid NSAIDs and review supplements

Strong evidence

Ibuprofen, naproxen and high-dose aspirin reduce kidney blood flow and are a leading cause of drug-related acute kidney injury, especially when combined with dehydration, diuretics or ACE inhibitors. Acetaminophen is the safer painkiller for most people with a raised creatinine. Some herbal products, notably those containing aristolochic acid, cause kidney damage and should be avoided entirely.

Do not stop prescribed medicines without talking to the prescriber; ACE inhibitors and SGLT2 inhibitors protect kidneys despite a small creatinine bump.

Moderate protein, mostly from plants

Moderate evidence

Very high protein intakes raise filtration pressure in the kidney and modestly increase creatinine. In established CKD, KDIGO guidelines recommend about 0.8 g/kg per day, and trials of plant-based protein show less acid load and less albuminuria than equivalent animal protein. For healthy adults the goal is simply to avoid sustained very high intakes.

Protein restriction below 0.6 g/kg should only be done with a renal dietitian.

When to see a clinician promptly

  • A creatinine that has risen by 0.3 mg/dL or more from your usual value within days, or by 50 percent or more within a week.
  • Passing very little urine for 8 to 12 hours, especially after vomiting, diarrhea, a new medicine or contrast dye.
  • Swelling of the legs or face, breathlessness, or chest discomfort together with a high creatinine.
  • Severe muscle pain and dark, cola-coloured urine after heavy exercise, a fall or starting a statin.
  • Inability to pass urine, or severe flank pain, which may mean a blockage.
  • A potassium above 5.5 mmol/L or a bicarbonate below 18 on the same report; these need action the same day.

Frequently asked questions

What is a normal creatinine level?

Most US labs report about 0.74 to 1.35 mg/dL for adult men and 0.59 to 1.04 mg/dL for adult women. Ranges differ between labs and depend heavily on muscle mass, so a muscular man may be normal at 1.4 and a frail woman abnormal at 1.0. The eGFR calculated from the creatinine is the more useful number.

Is a creatinine of 1.4 bad?

It depends who you are. For a 30-year-old muscular man, 1.4 mg/dL often gives an eGFR above 60 and may be normal for him. For a 70-year-old woman, 1.4 gives an eGFR near 38, which is stage 3b kidney disease. Look at the eGFR on your report, whether the value is new, and whether there is protein in your urine.

How can I lower my creatinine?

First find out why it is high. If it is dehydration, fluids will fix it within a day or two. If it is creatine, cooked meat or a medicine like trimethoprim, stopping that removes the artefact. If it is reduced kidney function, there is no supplement that lowers creatinine; the levers are blood pressure and blood sugar control, avoiding NSAIDs, moderate protein and a plant-forward diet, which protect the filtration you have.

Can dehydration raise creatinine?

Yes. Low fluid volume reduces blood flow through the kidneys so less creatinine is filtered. A stomach bug, a hot day or diuretics can raise creatinine by 0.2 to 0.5 mg/dL, with the BUN/creatinine ratio rising above 20. The value should return to baseline after rehydration; if it does not, the kidneys need a closer look.

Does creatine raise creatinine?

Yes, by about 0.1 to 0.3 mg/dL at a typical 3 to 5 g daily dose, and more during loading. This is because supplemental creatine is converted to creatinine, not because the kidneys are harmed. Large reviews find creatine safe for healthy kidneys, but it can make a lab result look worse than it is, so stop it for one to two weeks before testing and tell your clinician.

Why does eGFR matter more than creatinine?

Creatinine depends on muscle as much as on the kidneys, so the raw number cannot be compared between people. eGFR adjusts for age and sex and estimates how many millilitres of blood your kidneys filter per minute. Kidney disease is defined and staged by eGFR and urine albumin, not by creatinine alone.

What does low creatinine mean?

Low creatinine almost always reflects low muscle mass, not super-healthy kidneys. It is common in older adults, small-framed people, during pregnancy, with liver disease and after weight loss. It is rarely a problem itself, but it makes the eGFR look better than it is, so clinicians may add cystatin C to check.

Can exercise affect creatinine?

Intense or prolonged exercise in the day before a test can raise creatinine by 0.1 to 0.3 mg/dL through muscle breakdown and temporary dehydration. Regular training also builds muscle, which raises your baseline. For the cleanest reading, avoid hard workouts for 24 to 48 hours before the draw.

References

  1. Creatinine Test. MedlinePlus, US National Library of MedicineView source
  2. Creatinine test. Mayo ClinicView source
  3. Inker LA, Eneanya ND, Coresh J, et al.. New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race. New England Journal of Medicine (2021)View source
  4. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney International (2024)View source
  5. Preiss DJ, Godber IM, Lamb EJ, Dalton RN, Gunn IR. The influence of a cooked-meat meal on creatinine plasma concentration and estimated glomerular filtration rate. Annals of Clinical Biochemistry (2007)
  6. Nair S, O'Brien SV, Hayden K, et al.. Effect of a cooked meat meal on serum creatinine and estimated glomerular filtration rate in diabetes-related kidney disease. Diabetes Care (2014)
  7. Kreider RB, Kalman DS, Antonio J, et al.. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. Journal of the International Society of Sports Nutrition (2017)View source
  8. Clark WF, Sontrop JM, Huang SH, et al.. Effect of Coaching to Increase Water Intake on Kidney Function Decline in Adults With Chronic Kidney Disease: The CKD WIT Randomized Clinical Trial. JAMA (2018)View source
  9. Gaitonde DY, Cook DL, Rivera IM. Chronic Kidney Disease: Detection and Evaluation. American Family Physician (2017)
  10. Rebholz CM, Crews DC, Grams ME, et al.. DASH (Dietary Approaches to Stop Hypertension) Diet and Risk of Subsequent Kidney Disease. American Journal of Kidney Diseases (2016)
  11. Kelly JT, Palmer SC, Wai SN, et al.. Healthy Dietary Patterns and Risk of Mortality and ESRD in CKD: A Meta-Analysis of Cohort Studies. Clinical Journal of the American Society of Nephrology (2017)
  12. Estimated Glomerular Filtration Rate (eGFR). National Kidney FoundationView source

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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.