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Creatinine

Creatinine is a muscle waste product that your kidneys filter out, so the level in your blood is one of the main tools for checking kidney function.

AI-verified against cited sources. Awaiting expert reviewAlso called SCr, CREALOINC 2160-0

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What it is

Creatinine is made at a fairly steady rate as your muscles are used and repaired. Your kidneys filter it from the blood, and it leaves in your urine. If your kidneys filter less, creatinine builds up in the blood. The test is part of most routine blood panels, and it is used to calculate eGFR, an estimate of how well your kidneys are filtering.

Why it matters

Creatinine is the main blood test used to look at kidney function. Your level also depends on how much muscle you have, what you eat and how active you are, so your own usual level matters as much as the number itself. A result in the usual range does not always mean healthy kidneys, because creatinine can stay in range during the early stages of kidney disease. That is why clinicians also look at eGFR and urine tests.

If it’s low

A low creatinine is less common and usually reflects low muscle mass rather than a kidney problem. It can be expected in people who are small, older or frail. Less often it reflects poor nutrition or advanced liver disease.

Common causes

  • A small body frame or low muscle mass
  • Muscle loss with aging
  • A long illness or poor nutrition
  • A low-protein or vegetarian diet
  • Conditions that make muscles shrink, such as some nerve disorders
  • Advanced liver disease

What can help

  • Ask your clinician whether a low value fits your body size and muscle mass
  • If you are eating very little protein or losing weight without trying, mention it at your next visit

If it’s high

A high creatinine means less creatinine is leaving the blood than usual. That can be a sign that the kidneys are filtering less. It can also come from dehydration, a recent meat meal, creatine supplements, hard exercise or having a lot of muscle. One result is rarely enough to say what is going on, so clinicians usually look at eGFR, trends over time and other tests.

Common causes

  • Dehydration or low blood volume
  • A recent cooked meat or fish meal
  • Hard exercise or a large amount of muscle
  • Creatine supplements
  • Some medicines, such as trimethoprim, which can raise creatinine without lowering true kidney filtration
  • Reduced blood flow to the kidneys, as in heart failure
  • Kidney disease or injury, or a blockage in the urinary tract
  • Muscle injury (rhabdomyolysis)
  • Some health problems in pregnancy

What can help

  • Ask your clinician whether your recent meals, exercise, supplements or medicines could explain the result
  • Ask whether to recheck it and look at your eGFR
  • Ask whether a cystatin C test would help if your muscle mass is much higher or lower than average

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

The usual range depends on sex and age. Choose women or men to see the one that applies.

Children and teens 4 ranges

See Creatinine by age and sex, with the U.S. survey numbers where they exist.

If this applies to you

Creatinine means a little more for some people. Open the one that fits you.

Gout

eGFR is worked out from creatinine. The current allopurinol label lists creatinine and eGFR among the tests to check before starting it for gout, and warns that people with kidney disease or kidney stones may be at higher risk of kidney problems on it.

Blood tests for gout

Kidney disease or at risk

eGFR is worked out from creatinine, so anything that moves creatinine moves eGFR. KDIGO 2024 lists high muscle mass, high-protein diets, creatine supplements and a recent cooked meat or fish meal among the things that change creatinine without any change in the kidneys.

Blood tests for kidney health

Age 65 or older

Creatinine comes from muscle, so it runs lower when muscle mass is low. KDIGO says creatinine in older adults should be read with body build in mind, since muscle loss is common and can make a creatinine-based eGFR look better than kidney function really is.

Blood tests for older adults

Strength training

Creatinine comes from muscle, so more muscle, creatine supplements and high-protein diets can raise it without any change in how well the kidneys filter. In healthy people, a creatine-related rise is unlikely to mean kidney damage.

Blood tests for strength training and bodybuilding

On gender-affirming hormones

With spironolactone, WPATH suggests checking creatinine along with potassium to watch kidney function. Creatinine also reflects muscle mass, which shifts on hormones, so a 2021 review suggests reading it against the range of your affirmed gender once you've started hormones.

Blood tests on gender-affirming hormones

On a GLP-1 medicine

The labels describe kidney injury in some people, mostly after nausea, vomiting or diarrhea led to dehydration. They suggest checking kidney function in people who have side effects that could cause fluid loss.

Blood tests on GLP-1 medicines like Ozempic and Mounjaro

Taking HIV PrEP

Truvada (F/TDF) has caused small drops in kidney function that mostly reversed after stopping. The CDC suggests a kidney check before starting pills, then every 6 months for people 50 or older or with lower kidney function at the start, and every 12 months for everyone else. The CDC schedule for cabotegravir shots doesn't include kidney checks.

Blood tests on HIV PrEP

Taking lithium

Creatinine is the blood result eGFR is worked out from. The FDA label names creatinine for checking kidney function on lithium, and NICE suggests closer lithium checks if urea and creatinine rise.

Blood tests on lithium

Taking methotrexate

When the kidneys work less well, methotrexate is cleared more slowly and side effects become more likely. That is why creatinine is checked before starting and at every routine check.

Blood tests on methotrexate

How common is your level?

NHANES describes the US civilian, non-institutionalized population, not a 'healthy' reference group. People with disease, on medication, fasting or not (except fasting-subsample markers), smokers and so on are all included. A percentile says where a value sits among Americans of that sex and age, not whether it is normal.

How Creatinine varies with age in the U.S.Shaded: middle 90% and middle 50% of people. Line: the median. mg/dL. Point at any age, or focus the chart and use the arrow keys, to read both sexes in words.

Use the left and right arrow keys to read each age. Shift moves five years.

Reference data derived from CDC/NCHS National Health and Nutrition Examination Survey (NHANES), cycles 2015-2016, 2017-March 2020 (pre-pandemic), August 2021-August 2023. Analysis by bloodtesttracker.com; not endorsed by CDC, NCHS or HHS.

Explore Creatinine by age and sex: every percentile as a table, with a download.

What can affect your result

  • Muscle mass: more muscle means a higher creatinine, and less muscle means a lower one
  • Sex: men usually have higher levels than women, partly because of more muscle
  • Age: children have much lower levels, and older adults often have less muscle
  • Diet: cooked meat and fish, high-protein diets and creatine supplements can raise it
  • Hard exercise and muscle injury can raise it
  • Hydration: dehydration can raise it
  • Some medicines and lab methods can change the result
  • Day-to-day variation from diet and activity can be as large as 10%, and results from different labs can differ further
  • A cooked meat or fish meal can temporarily raise creatinine (about 0.23 mg/dL in one study cited by KDIGO). The effect peaks by about 2 to 4 hours, and waiting 12 hours after eating meat or fish best avoids it.
  • Creatine supplements, high-protein diets and a lot of muscle can raise creatinine without any change in kidney function. Low muscle mass, low-protein and vegetarian diets can lower it.
  • Hard exercise and muscle injury can raise creatinine.
  • Trimethoprim can raise creatinine by blocking its release into the urine, without lowering true kidney filtration, and cimetidine is also listed as affecting creatinine results. Cephalosporin antibiotics can falsely raise results on Jaffe methods when the sample is drawn within about 4 hours of a dose.
  • On Jaffe methods, very high glucose (above about 450 mg/dL), bilirubin, hemolysis or lipemia can skew results.
  • High levels of N-acetylcysteine (NAC) can falsely lower results on enzymatic assays.

Creatinine climbs over several days after a sudden drop in kidney filtration rather than all at once. KDIGO defines acute kidney injury as a rise of 0.3 mg/dL or more within 48 hours.

When to talk to a clinician

Talk with your clinician soon if your creatinine is above your lab's range, especially if it is higher than your earlier results. Clinicians define a sudden kidney injury as a rise of 0.3 mg/dL (26.5 µmol/L) or more within 48 hours, or a rise to 1.5 times your usual level within a week, so a jump like that deserves a prompt call. Get care if you pass much less urine than usual, or have swelling in your legs or face, or nausea and unusual tiredness. Call 911 or your local emergency number for chest pain, trouble breathing, confusion or fainting.

Questions you could ask

  • How does my creatinine compare with my past results?
  • Do any of my medicines or supplements affect my creatinine?
  • Could my recent meals, exercise, supplements or medicines explain this result?
  • Should we recheck my creatinine and look at my eGFR?
  • Would a cystatin C test or a urine test help?
  • Does this fit with my body size and muscle mass?

Questions people ask

Can my creatinine be in the usual range if I have kidney disease?

Yes. Creatinine can stay in the usual range during the early stages of kidney disease and rise only as kidney function falls further. That is why clinicians also use eGFR and urine tests, such as the urine albumin-to-creatinine ratio, when they are checking your kidneys.

Can lifting weights, creatine or eating meat raise my creatinine?

Yes. A cooked meat or fish meal, creatine supplements, a high-protein diet and a lot of muscle can all raise creatinine without any change in how well your kidneys filter. If this might apply to you, tell your clinician. They may suggest a retest or a cystatin C test, which does not depend on muscle.

How do I convert creatinine from mg/dL to µmol/L?

Multiply mg/dL by 88.4, so 1.0 mg/dL is about 88 µmol/L. To go the other way, divide µmol/L by 88.4. Some labs print mg/L instead, which is 10 times the mg/dL value.

Why do different labs show different ranges?

Labs use different methods and their own reference groups. For adult men, Mayo Clinic Laboratories uses 0.74–1.35 mg/dL and Labcorp uses 0.76–1.27 mg/dL, for example. Compare your result with the range printed on your own report.

What is the difference between creatinine and eGFR?

Creatinine is a level measured in your blood. eGFR is an estimate of how well your kidneys filter, calculated from your creatinine plus your age and sex. Many US labs use the 2021 CKD-EPI equation, which does not use race.

Show the science and sources

Units

  • 1 mg/dL = 1 mg/dL
  • 1 mg/dL = 88.4 µmol/L
  • 1 mg/dL = 10 mg/L

Open the Creatinine unit converter

Is a change real?

Creatinine naturally varies about 4.5% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 14% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: Critical appraisal and meta-analysis of biological variation estimates for kidney related analytes (Jonker N et al., EFLM WG-BV).

For clinicians and researchers

Creatinine (113.12 g/mol) forms from creatine and phosphocreatine in muscle at a roughly constant rate. It is freely filtered and not reabsorbed, and a small share is secreted by the tubules. That secretion is why some drugs, such as trimethoprim, raise serum creatinine without lowering GFR (KDIGO 2024 lists reversible inhibition of tubular creatinine secretion for sulfamethoxazole-trimethoprim; KDIGO 2012 also lists cimetidine among drugs that affect creatinine results). It is a delayed and insensitive marker. In chronic progressive disease it becomes abnormal only after about half or more of nephron function is lost (Labcorp). In acute injury it can rise by up to about 2 mg/dL per day depending on muscle mass and body water (Merck Manual), and KDIGO defines AKI by a rise of 0.3 mg/dL within 48 hours or 1.5 times baseline within 7 days. Its non-GFR determinants include muscle mass, diet (a cooked meat meal), creatine supplements, tubular secretion and assay interference. KDIGO 2024 therefore advises reading creatinine with dietary intake in mind and considering cystatin C (eGFRcys or eGFRcr-cys) when eGFRcr is likely to be inaccurate. Jaffe (alkaline picrate) methods, as at Labcorp, show positive interference from cephalosporins drawn within 4 hours of a dose and from glucose above 450 mg/dL (about +16%), and Labcorp notes interference from bilirubin, hemolysis and lipemia. KDIGO 2012 also lists bilirubin, ascorbic acid and uric acid as endogenous chromogens. Enzymatic methods, as at ARUP, are generally more specific but show negative interference from N-acetylcysteine and, at overdose levels, NAPQI. Within-lab imprecision is small (under 5%), but bias between labs can be considerably larger. International standardization of creatinine assays to isotope-dilution mass spectrometry (IDMS) reference materials is meant to reduce that bias. Mayo Clinic Laboratories calculates eGFR with the 2021 CKD-EPI creatinine equation, which no longer includes race, and KDIGO 2024 advises against using race in eGFR. SI conversion: µmol/L = mg/dL × 88.4. Some labs, for example in France, report mg/L, which is mg/dL × 10.

LOINC 2160-0 (primary), 14682-9, 38483-4, 59826-8, 35203-9. Specimen: serum-or-plasma.

Sources

  1. Creatinine with Estimated Glomerular Filtration Rate (eGFR), Serum (test ID CRTS1), Mayo Clinic Laboratories (test catalog copy hosted by Schneck Medical Center)
  2. Creatinine (test 001370), Labcorp
  3. Creatinine, Serum or Plasma (test 0020025), ARUP Laboratories
  4. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease, Kidney International Supplements (2024)
  5. KDIGO Clinical Practice Guideline for Acute Kidney Injury, Kidney International Supplements (2012)
  6. Creatinine Test, MedlinePlus (National Library of Medicine)
  7. Acute Kidney Injury (AKI), Merck Manual Professional Edition, Merck Manual (2026)
  8. Creatinine (PubChem CID 588), molecular weight 113.12, PubChem (National Library of Medicine)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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