Does creatine affect your blood test results?
Short answer: yes, it can. Creatine supplements raise creatinine, the waste product used to estimate kidney function (eGFR). That can make your kidneys look as if they are working less well than they really are. Tell the clinician that you take creatine, and ask whether a cystatin C test would help.
Why creatine changes the result
Your body turns creatine into creatinine, which the kidneys clear. eGFR is calculated mainly from creatinine, so extra creatine, a lot of muscle or a large cooked-meat meal can all push creatinine up and eGFR down, even when the kidneys are healthy. See the creatinine test and the kidney health profile.
A second check: cystatin C
Cystatin C is much less affected by muscle and creatine, so it can give a second estimate of kidney function when creatinine may be misleading. See the cystatin C test.
Hard exercise matters too
Heavy training in the day or two before a test can raise creatine kinase, a muscle enzyme, and sometimes liver enzymes such as AST and ALT. See the creatine kinase test.
Is creatine bad for your kidneys?
In healthy adults taking usual doses, research has not shown that creatine damages the kidneys. If you have kidney disease, diabetes or take medicines that affect the kidneys, speak to a clinician before using it.
How to prepare for a kidney test
Tell the clinician that you take creatine and how much
Ask whether you should pause it for a period before a repeat test
Avoid hard exercise and a very large meat meal the day before
Drink normally so that you are not dehydrated
Frequently asked questions
Will creatine make my result look abnormal?
It can flag a raised creatinine or a lower eGFR. A clinician will interpret it knowing that you take creatine.
Should I stop creatine before every blood test?
Not necessarily. It matters mostly for kidney tests. Ask the clinician what is right for your situation.
Does creatine affect other blood tests?
It has little effect on most other routine tests. Training itself has more effect, especially on muscle enzymes.
Sources
NICE guideline NG203: chronic kidney disease, assessment and management
International Society of Sports Nutrition position stand on creatine supplementation
Related reading
Clinically reviewed by Zak Toon, ACP, on 15 October 2026.
This article is general information based on UK guidance. It is not personal medical advice. If you are worried about your health or have symptoms, speak to your GP or call 111.
