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Creatine vs Creatinine: Why a Supplement Can Change a Blood Test
They are not the same thing. Creatine is the compound your muscles store for short bursts of effort; creatinine is the waste product it breaks down into, and the one a kidney blood test measures. Taking creatine raises the creatinine reading within days while measured kidney filtration does not change, so tell your GP you take it before a blood test. The guide to what creatine does covers the muscle side; this page covers the test.
Creatine vs creatinine: what is the difference?
Creatine is made in the liver and kidneys from amino acids, arrives in meat and fish, and is stored in muscle as phosphocreatine for the first seconds of hard effort. It is the supplement.
Creatinine is what creatine and phosphocreatine become as they break down, steadily and without any enzyme. It passes into the blood, the kidneys filter it out and it leaves in urine.1 So the amount in the blood is a proxy for how well the kidneys filter: the NHS describes the main kidney test as measuring "a waste product called creatinine in your blood".2
A results letter reading "creatine 91" means creatinine, in micromoles per litre; blood creatine is not on a routine panel.
Creatine, creatinine and creatine kinase: three different things
Creatine kinase (CK, or creatine phosphokinase) is a muscle enzyme that moves phosphate on and off creatine and leaks into the blood when muscle fibres are damaged, so it is checked after injury, heavy training or statin muscle pain. Creatine does not raise it: a 21-month panel of muscle and liver enzymes in 98 athletes found no difference.3 A raised creatine kinase is a question about your muscles for your GP; this page stops there.
How does creatine turn into creatinine?
In proportion to how much you carry. In a 1996 study of 31 men, muscle creatine rose about 20% over 28 days at 3 g (grams) a day, or in six days at 20 g; after stopping, stores fell back to baseline over 30 days and urinary creatinine rose as they did.1 A bigger store means a bigger daily trickle of creatinine. Blood creatinine also tracks muscle mass (men run higher than women) and rises after meat, which carries both compounds.4 Creatine that degraded in a drink left standing or a warm gummy arrives as creatinine (see whether creatine gummies work).
| Test | What it measures | What moves it | Does creatine move it? |
|---|---|---|---|
| Serum creatinine | The waste product in blood | Muscle mass, meat, filtration, supplements | Yes, a small rise |
| eGFR | Estimate from creatinine, age, size, sex | Whatever moves creatinine | Yes, downwards, by arithmetic |
| Cystatin C | A filtered protein, not from muscle | Filtration | No (2008 trial) |
| Tracer clearance | Filtration, directly | Filtration | No (2011 trial) |
| Creatine kinase | A muscle enzyme | Muscle damage, hard training | Not in the trials |
Does taking creatine raise your creatinine level?
Yes, within days. In a five-day trial of 54 men on 20 g a day, serum creatinine rose in every creatine group and not on placebo.5 A 2025 review pooled 12 trials (177 on creatine, 263 controls): a small, significant rise, present at a week or less and again beyond 12 weeks but not between, with no difference in glomerular filtration rate; the authors read it as metabolic turnover, not kidney impairment.6
How much? We do not print the review's figure, because its abstract gives it in a unit that cannot be right at that size. Every trial supports a small rise, typically still inside the normal range in a healthy adult, but enough to tip a borderline estimate.
Does creatine affect eGFR or a kidney function test?
It affects the estimate, not the kidney. The NHS explains that a doctor uses your creatinine result "plus your age, size, and gender" to calculate how many millilitres your kidneys filter a minute; healthy kidneys filter "more than 90ml/min".2 Anything that raises creatinine lowers that estimate. Creatine raises the number a kidney test reads without changing what the kidney does, in every trial that measured both; the fix is a sentence to your GP.
Filtration itself has been measured three other ways. Cystatin C, a marker not made in muscle, fell in both groups in 18 men on about 10 g a day for three months, 0.82 to 0.71 mg/L on creatine, a sign of filtration improving with training; serum creatinine fell on placebo and held level on creatine.7 A tracer clearance test (51Cr-EDTA) in people with type 2 diabetes over 12 weeks: 90.4 to 96.1 mL/min/1.73 m² on creatine, 97.9 to 96.4 on placebo, no difference.8 Twenty-one months of blood and urine markers in 98 athletes: no significant differences.3
Three kidney case reports are indexed on PubMed, each with a confounder. A 1998 letter described a young man whose creatinine rose on creatine after eight years of kidney disease and five on ciclosporin, an immunosuppressant.4, 9 A 1999 letter reported interstitial nephritis in a man taking creatine.10 In 2006 a 24-year-old taking creatine and several other supplements developed acute kidney failure with biopsy-proven interstitial nephritis and recovered completely when he stopped them all.11 A 2004 review added one case at 20 g a day for four weeks and concluded that kidney disease, or medicines that load the kidneys, may raise the risk.12 If that is you, the renal team comes first and no trial covers you; the same goes for long-term anti-inflammatory painkillers such as ibuprofen, or diuretics. The kidney question for people who also take collagen is in collagen and creatine together.
Should you stop creatine before a kidney blood test? What to tell your GP
No source sets a stop-before rule and no trial has timed how fast blood creatinine falls after stopping, so a week off has no data behind it and may leave the reading raised. Muscle stores take about four weeks to return to baseline (what happens when you stop taking creatine).1 The NHS's own instruction, on the one NHS page that names creatine: the supplement "can affect the results of your kidney function tests", so "let your clinic doctor know".13
To the GP: "I take 3 to 5 g (grams) of creatine monohydrate a day as a supplement; it raises blood creatinine without changing kidney function, and I understand it can lower an estimated GFR." To the practice nurse: "Please note on the form that I take creatine; it raises creatinine." To the pharmacist: "I take creatine; please flag it for whoever reads my kidney results." If a repeat test is wanted, the GP decides how long off; cystatin C is an alternative marker a GP may choose, because creatine does not move it.7
That 3 g a day is the condition on the one wording UK law allows: creatine increases physical performance in successive bursts of short-term, high intensity exercise, for adults doing high-intensity exercise. Drink as you normally would; the NHS guide is 6 to 8 cups or glasses of fluid a day, more in heat or during long sessions (see does creatine dehydrate you). A fasting instruction is about food; the rise comes from weeks of stores, not one dose. How much creatine to take is its own page.
What if your creatinine reading is already high?
Speak to your GP first. A high reading from before you ever took creatine is a medical question this page does not answer. If it rose after you started creatine, say the sentence above.
Some readers take creatine because their creatinine was low. The reading is a waste product, not a store to top up: a low value usually reflects less muscle mass, and creatine would raise the number without changing anything it stands for.4 Why doctors are sometimes cautious is on creatine side effects. Nor is creatine the only supplement that moves a result: too much vitamin D raises blood calcium (can you take too much vitamin D).
Frequently asked questions
Is creatinine the same as creatine?
No. Creatine is the compound your muscles store and the supplement you buy; creatinine is the waste product it turns into, which a kidney blood test measures.
Can creatine supplements affect eGFR?
Yes, by raising the creatinine it is calculated from. Filtration measured directly, by cystatin C or a tracer, did not change in the trials.7, 8
Can creatine affect a DEXA scan?
Yes. In 13 dancers over 42 days, total body water rose from 32.2 to 32.7 kg and DEXA lean mass from 39.8 to 41.5 kg; the scan reads water inside muscle as lean tissue, and the authors wanted larger trials before calling it muscle.14
Does exercise or a steak dinner change a creatinine test?
Meat does, because it carries creatine and creatinine, and reviewers warn against reading an eGFR in heavy meat eaters without allowing for it.4 A GP will also ask about hard training in the day or two before; mention both, with the supplement.
Can taking creatine make your eGFR look low enough for a kidney disease label?
It can nudge a borderline estimate under the NHS's "more than 90ml/min" line.2 That is a reason to say you take creatine, not to panic: the NHS says let the doctor know, and filtration measured directly did not change.8, 13
Sources
- Hultman E, et al. Muscle creatine loading in men. Journal of Applied Physiology, 1996. PubMed 8828669.
- NHS. Chronic kidney disease: diagnosis. Reviewed 22 March 2023; fetched 11 October 2026. nhs.uk.
- Kreider RB, et al. Long-term creatine supplementation does not significantly affect clinical markers of health in athletes. Molecular and Cellular Biochemistry, 2003. PubMed 12701816.
- Antonio J, et al. Common questions and misconceptions about creatine supplementation: what does the scientific evidence really show? Journal of the International Society of Sports Nutrition, 2021. PubMed 33557850.
- Trexler ET, et al. Effects of coffee and caffeine anhydrous intake during creatine loading. Journal of Strength and Conditioning Research, 2016. PubMed 26439785.
- Naeini EK, et al. Effect of creatine supplementation on kidney function: a systematic review and meta-analysis. BMC Nephrology, 2025. PubMed 41199218.
- Gualano B, et al. Effects of creatine supplementation on renal function: a randomized, double-blind, placebo-controlled clinical trial. European Journal of Applied Physiology, 2008. PubMed 18188581.
- Gualano B, et al. Creatine supplementation does not impair kidney function in type 2 diabetic patients: a randomized, double-blind, placebo-controlled, clinical trial. European Journal of Applied Physiology, 2011. PubMed 20976468.
- Pritchard NR, et al. Renal dysfunction accompanying oral creatine supplements. The Lancet, 1998. PubMed 9643752.
- Koshy KM, et al. Interstitial nephritis in a patient taking creatine. New England Journal of Medicine, 1999. PubMed 10075534.
- Thorsteinsdottir B, et al. Acute renal failure in a young weight lifter taking multiple food supplements, including creatine monohydrate. Journal of Renal Nutrition, 2006. PubMed 17046619.
- Yoshizumi WM, et al. Effects of creatine supplementation on renal function. Journal of Herbal Pharmacotherapy, 2004. PubMed 15273072.
- NHS. Taking PrEP with other medicines and herbal supplements. Reviewed 10 March 2023; fetched 11 October 2026. nhs.uk.
- Brooks SJ, et al. Creatine monohydrate supplementation changes total body water and DXA lean mass estimates in female collegiate dancers. Journal of the International Society of Sports Nutrition, 2023. PubMed 36960692.
