Creatinine — Glossary | Creatine.my

Written by Creatine.my Editorial Team · · 3 min read
3 min read

What is Creatinine?

Creatinine is a metabolic waste product formed from the non-enzymatic breakdown of creatine and phosphocreatine in muscle tissue.

Approximately 1.7% of the body’s total creatine pool is converted to creatinine daily through spontaneous dehydration.

Creatinine is released into the bloodstream, filtered by the kidneys, and excreted in urine.

In clinical medicine, serum creatinine levels are commonly used as a marker of kidney function, specifically to estimate glomerular filtration rate (GFR).

This is where confusion arises for creatine users.

The Blood Test Confusion

Because creatine supplementation increases the body’s total creatine pool, it also increases the rate of creatinine production.

This results in elevated serum creatinine levels that can be misinterpreted as impaired kidney function.

Key points:

  • Creatine supplementation raises creatinine by approximately 10-20%
  • This elevation is not pathological — it reflects increased creatine turnover, not kidney damage
  • GFR estimates based on creatinine may be falsely low in creatine users
  • Alternative markers like cystatin C provide more accurate kidney function assessment for supplement users

Relevance to Creatine Supplementation

Understanding creatinine helps creatine users navigate medical situations:

  • Inform your doctor about creatine use before blood tests
  • Do not panic if creatinine levels are slightly elevated
  • Request cystatin C testing if accurate kidney function assessment is needed
  • Long-term studies consistently show that creatine does not damage healthy kidneys despite elevated creatinine
  • Creatine Kinase — The enzyme system involved in creatine-phosphocreatine cycling
  • Phosphocreatine — The energy-storage form that partially converts to creatinine
  • Bioavailability — How much supplemental creatine reaches muscles vs. being converted to creatinine

Sources & References

Full citations available in our Research Library.

Frequently Asked Questions

Does creatine supplementation raise creatinine levels?

Yes. Creatine supplementation typically raises serum creatinine by 10-20%. This is a normal consequence of increased creatine metabolism, not a sign of kidney damage. If you are getting blood tests, inform your doctor that you take creatine so they can interpret creatinine levels accurately.

What is the difference between creatine and creatinine?

Creatine is a beneficial compound stored in muscles for energy production. Creatinine is the waste product formed when creatine and phosphocreatine break down. Creatinine is filtered by the kidneys and excreted in urine. They are chemically related but serve completely different functions.

Should I stop creatine before a blood test?

It depends on the purpose of the test. If kidney function is being assessed, stopping creatine 2-3 weeks before testing gives a more accurate baseline creatinine reading. Alternatively, inform your doctor about your creatine use so they can use cystatin C or other markers for a more accurate kidney function assessment.

Reviewed by T. Dinaiz, BSc (Molecular Biology), MSc (Biotechnology)

Reviewed against peer-reviewed research · Our editorial policy