Creatine and Protein Powder: More Info Before Starting these Supplements
- Carly Valencia-Ochoa, MD
- 9 minutes ago
- 4 min read
Carly Valencia-Ochoa, MD
Creatine (the exercise supplement)
What it is and why people take it
Creatine monohydrate helps build muscle strength and is widely used by athletes and older adults to preserve muscle mass.
What it does to the labs and kidneys
Creatine breaks down into creatinine, so taking creatine commonly ↑ increases serum creatinine. That can make eGFR appear worse, even if kidney function hasn’t changed. This can lead to unnecessary worry or extra tests unless your clinician knows you’re taking creatine.
In otherwise healthy individuals, numerous studies have shown no clear evidence that the usual dose of creatine (3–5 g/day maintenance) causes kidney damage. But evidence in people with existing CKD or on nephrotoxic medications is limited/uncertain so most guidance is conservative.

Practical advice
If you have NO kidney disease and want to try creatine: discuss with your primary care provider, use typical maintenance doses (3–5 g/day), and choose a triple-tested brand. Expect a possible rise in serum creatinine; inform any healthcare provider wh o orders labs that you take creatine.
If you have CKD, reduced eGFR, proteinuria (protein in the urine), are on ACEi/ARB/diuretics, or take nephrotoxic drugs: don’t start creatine without nephrology approval. Your kidney team may recommend avoiding it or doing closer lab monitoring (serum creatinine, BUN, electrolytes, urinalysis).
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Protein powders (whey, casein, soy, pea, etc.)
What patients worry about
“Will protein powder damage my kidneys?” “How much is too much?” “Which type is better (animal vs plant)?”
What the evidence says (recent findings)
Total daily protein matters. In people with CKD, particularly in later stages, high protein loads can raise intraglomerular pressure and potentially accelerate kidney injury. Recent analyses show complex relationships — some older adults with mild/moderate CKD had better survival with higher protein, so it’s not one-size-fits-all.
Quality matters. Plant proteins may have advantages (lower acid load, less phosphorus absorption), whereas some animal proteins and processed protein products can contain additives or a higher phosphorus burden.
Contaminants & additives. Some powders may contain added potassium, phosphorus, creatine, caffeine, sugars, or trace contaminants (such as heavy metals) in certain brand batches — it's best to opt for third-party tested products.
Practical advice
Count protein powder toward your daily protein goal. If your kidney team advised a specific protein target (for example, 0.6–0.8 g/kg/day for some CKD patients), include supplements in that total.
If you have early CKD (mild) and are older or frail, protein supplements may sometimes be recommended to prevent malnutrition — but only with dietitian guidance.
If you have moderate–advanced CKD (eGFR <60, especially <30): avoid adding large amounts of protein powder unless prescribed/monitored. Work with a renal dietitian to determine the type (plant-based vs. whey), amount, and timing.
Choose quality products: Look for third-party testing seals (e.g., NSF, USP, Informed-Sport), low added sugar, and check ingredient lists for phosphate additives, high sodium or high potassium or unwanted stimulants.
Things your physician will likely monitor if you use these supplements
Serum creatinine & eGFR (but know creatine can raise creatinine unrelated to filtration).
BUN, electrolytes (potassium, phosphorus), uric acid (can be affected by high-protein diets), and urine albumin/protein.
Weight, muscle mass, and symptoms of fluid overload or malnutrition.
Practical scenarios
You’re a healthy 25-year-old athlete: creatine 3–5 g/day is commonly considered safe; consult your doctor before taking any supplements. Use protein powder if your overall daily protein limit allows it.
You’re a 70-year-old with eGFR 45 (stage 3a CKD): don’t add large protein powders without dietitian input — you may need moderate protein to prevent sarcopenia, so a tailored plan is best.
You have eGFR 25 (stage 4 CKD): avoid unsupervised creatine and high-dose protein powders. Talk with your kidney team and a renal dietitian
Quick Summary:
Creatine: Widely studied and generally safe for healthy people, but it raises blood creatinine (the lab number doctors use to estimate kidney function), which can confuse eGFR results. People with known CKD or on nephrotoxic drugs should be cautious and check with their kidney doctor before starting creatine.
Protein powder: Can be useful (e.g., to prevent muscle loss), but it increases total protein intake. In some stages of CKD, you need guidance about protein intake. Choose quality products (third-party tested), watch serving sizes, and work with a renal dietitian.

Bottom line
Don’t assume supplements are harmless: they can change labs (especially creatine).
Healthy people: creatine and responsible protein powder use are often safe.
People with CKD: be cautious — discuss with nephrology and a renal dietitian before starting; monitor labs if used.

References
Zhou B, et al. Exploring the relationship between creatine ... (review). 2024. PMC
Marini ACB, et al. Effect of Creatine Supplementation on Body Composition ... Nutrients. 2024 — notes creatine can raise serum creatinine. MDPI
Vega J. Effects of creatine supplementation on renal function (review). 2019 — commonly cited caution that CKD patients should avoid supplements without supervision. PubMed
Patel V, et al. Protein supplementation: the double-edged sword. 2023 (review on protein and kidney implications). PMC
Carballo-Casla A, et al. Protein Intake and Mortality in Older Adults With CKD. JAMA Netw Open. 2024. (shows complexity of protein needs in older adults with CKD). JAMA Network
Consumer safety & supplement contamination overviews (reports & articles summarizing third-party testing recommendations).