Can creatine supplements cause kidney damage and hematuria?

Creatine Supplements and Kidney Safety

Creatine supplementation does not cause true kidney damage or hematuria in healthy individuals, but it artificially elevates serum creatinine levels, which can falsely suggest kidney dysfunction when using standard eGFR calculations. 1, 2

Key Distinction: Laboratory Artifact vs. Actual Kidney Damage

The critical issue with creatine supplementation is diagnostic confusion, not nephrotoxicity:

• Creatine supplementation increases serum creatinine without affecting actual kidney function, as demonstrated in a prospective case where creatinine rose from 1.03 to 1.27 mg/dL while measured GFR by 51Cr-EDTA clearance remained completely unchanged at ~82 mL/min/1.73m². 2

• eGFR formulas are invalid during creatine supplementation because they assume steady-state creatinine production and are unreliable in patients with high muscle mass or altered creatine metabolism. 1

• This creates a false appearance of acute kidney injury that can lead to misdiagnosis of chronic kidney disease when none exists. 3, 1

Evidence of Safety in Healthy Populations

Multiple controlled clinical trials demonstrate no actual kidney damage from creatine:

• Short-term (5 days) to long-term (5 years) supplementation at doses ranging from 5-30 g/day showed no significant effects on glomerular filtration rate, proteinuria, or other kidney function markers in healthy athletes. 4

• Even in a high-risk scenario—a young man with a single kidney taking 20 g/day for 5 days followed by 5 g/day for 30 days—measured GFR remained stable, proteinuria was unchanged, and electrolytes were normal. 2

• Systematic reviews of controlled trials consistently find creatine supplements safe for healthy individuals when used appropriately. 5, 6

Hematuria: Not a Documented Effect

There is no evidence linking creatine supplementation to hematuria:

• The guideline literature mentions creatine only in the context of potential rhabdomyolysis (which could secondarily cause hematuria), but this is exceedingly rare. 3, 7

• No clinical trials or case series document hematuria as a direct effect of creatine supplementation. 4, 5, 6

• If hematuria occurs in someone taking creatine, investigate for other causes—it is not attributable to the supplement itself.

When Creatine Should Be Avoided

Despite safety in healthy individuals, creatine supplementation should be avoided in specific populations:

• Pre-existing chronic kidney disease: Individuals with established renal dysfunction should not use creatine supplements. 5, 8

• Risk factors for kidney dysfunction: Those with diabetes, hypertension, or reduced baseline GFR should avoid high-dose creatine (>3-5 g/day). 5

• Concurrent nephrotoxic medications: Patients taking NSAIDs or other potentially nephrotoxic drugs should exercise caution. 3

• Kidney donors: Guidelines specifically discourage dietary supplement use in this population due to their solitary kidney status and need to preserve remaining renal function. 3

Proper Assessment When Creatine Use is Suspected

If a patient on creatine shows elevated creatinine, follow this algorithm:

1. Discontinue creatine immediately and wait 1-2 weeks before reassessing kidney function. 1

2. Obtain urinalysis with microscopy looking for proteinuria, hematuria, cellular casts, or acanthocytes that would indicate true intrinsic kidney disease. 1

3. Check spot urine albumin-to-creatinine ratio, as albuminuria indicates glomerular damage and true kidney disease. 1

4. Consider cystatin C measurement as an alternative marker of kidney function that is not affected by muscle mass or creatine supplementation. 1

5. Measure 51Cr-EDTA clearance or iothalamate clearance if available, as these provide true GFR measurement independent of creatinine. 2

6. Remember that CKD requires evidence of kidney damage or reduced GFR persisting for at least 3 months—a single elevated creatinine in the context of creatine supplementation does not establish CKD diagnosis. 1

Common Pitfalls to Avoid

• Do not diagnose kidney disease based solely on elevated serum creatinine in someone taking creatine—this is a laboratory artifact, not true renal dysfunction. 1, 2

• Do not use 24-hour urine creatinine clearance as it is less accurate than prediction equations and subject to collection errors, and will be falsely low during creatine supplementation. 1

• Do not assume that increased urinary methylamine and formaldehyde (metabolites of creatine) indicate kidney damage—these remain within normal ranges and have no proven adverse effects on kidney function. 5

• Recognize that creatine supplementation can cause 1-2 kg weight gain from water retention, which is benign but may concern patients. 7