Key Topics Covered

  • In the fitness world, we do see a lot of concern regarding creatine and kidney function since creatine is filtered through the kidneys, this can also result in abnormal kidney function results on a blood test.
  • Many people don’t take it for that reason and/or sometimes are told by medical professionals to stop taking it.
  • So today we are going to unpack that 

Mechanism

  • Creatine breaks down into creatinine. This is then excreted by the kidneys.
  • Creatinine levels are often used as a marker of kidney function.
  • This is because creatinine levels building up in the blood is often a sign that the kidneys are not functioning effectively.

General Creatine Safety

  • While this is normally a marker, in this case the creatinine levels are just “falsely” elevated due to this breakdown from creatine into creatinine. 
  • In people with healthy kidneys, it is totally safe.

Evidence That It Is Safe in Healthy Individuals

  • A relatively old study titled “Long-term oral creatine supplementation does not impair renal function in healthy athletes” explored the research and found that it does not increase the rate of decline in kidney function.
  • We are often hesitant to reference studies that old, but creatine has been studied for such a long time now. New research hasn’t given any reason to change that belief either. 


Blood Testing Issues

  • One issue is that it can “mask issues.” For example, if somebody WAS going to have elevated creatinine levels regardless, it could get brushed off due to creatine supplementation.
  • Two ways to get around this: 1) Drop creatine supplementation 30 days before a test 2) You could just test cystatin C to get eGFR instead which gets around the creatinine issue.
  • For what it’s worth, people with a lot of muscle mass and/or high training loads often run into similar issues without creatine supplementation anyway, so knowing about cystatin C is worthwhile.

What About Low Kidney Function?

  • For those with low kidney function, we understand the need for more caution. 
  • The logic simply would be that because the kidneys are struggling with filtering out waste products, it doesn’t makes sense to add more to that burden.
  • In the links below we have added a bunch of studies looking at this. They range from looking at older adults with CKD through to people who have recently undergone transplants, and none have identified issues.
  • It’s another area where people say “more research is needed” but it has also been studied for decades with no issues that have been found consistently as of yet.

Summary:

  • Creatine is super safe, which is part of why it is so commonly recommended.
  • Caution should be taken where there is already low kidney function and even where there is no known issue with the kidneys, it is often a good idea to just be sure by either stopping creatine and re-testing or looking at cystatin C.
  • But overall, creatine is safe for those with healthy kidneys.

Relevant Blogs/Research

Relevant blogs:

Relevant studies: