High creatinine: what it means and what to do next

Dr. Joan J. Morales Lappot, MD
3 min read · Leer en español

In briefA creatinine result flagged "high" is one of the most common reasons patients are sent to me. Sometimes it signals a kidney problem. Sometimes it is a temporary blip.

What creatinine is

Creatinine is a waste product made by your muscles every day. Healthy kidneys clear it steadily, so its level in the blood stays stable. When the kidneys filter less, creatinine builds up. Labs use it, with your age and sex, to estimate your eGFR.

Reasons it can be high without lasting damage

• Dehydration on the day of the test
• A large meat meal or intense exercise shortly before
• Having a lot of muscle
• Creatine supplements
• Certain medicines, such as trimethoprim, that change how creatinine is measured or cleared

Reasons that need attention

• A sudden kidney injury from illness, low blood pressure, dehydration or medicines
• Chronic kidney disease, often from diabetes or high blood pressure
• A blockage of urine flow, such as an enlarged prostate
• Inflammation of the kidney filters

What happens next

One number is not a diagnosis. Usually we repeat the test, compare it with older results, check a urine test for protein and blood, and review your medicines. Sometimes a kidney ultrasound helps. The pattern over weeks and months tells us far more than a single value.