Maybe you saw it in your patient portal before your doctor even called: creatinine, with an H next to it. Creatinine is a waste product left over when your muscles use creatine for energy, and some of it comes from digesting the protein you eat. Your kidneys filter it out of your blood and into your urine, so doctors use the amount in your blood to estimate how well your kidneys are filtering, a number called eGFR. MedlinePlus, the National Library of Medicine's health site, puts a normal result at 0.7 to 1.3 mg/dL for men and 0.5 to 0.95 for women, who usually carry less muscle. Ranges vary a little from lab to lab.

MedlinePlus also says a single high creatinine test can't diagnose a specific condition. The National Kidney Foundation (NKF) lists things that can push the reading up: large amounts of cooked meat, creatine supplements, a recent hard workout, a lot of muscle, and some medicines, such as the antibiotic trimethoprim. Dehydration can do it too. In a 2026 review of 19 trials, mostly in healthy, active people, creatine supplements raised the reading by about 0.13 mg/dL on average, with no significant change in eGFR. (For people who already have kidney disease, the NKF lists creatine as high-risk.) Doctors usually recheck the number, look at your eGFR, and add a urine test for albumin. Chronic kidney disease means low kidney function or damage that lasts three months or more, confirmed by repeat tests.

Start with your doctor. They can work out what pushed your number up. Tell them if you've noticed puffy eyelids, swollen hands or feet, foamy or bloody urine, or shortness of breath. Mention every supplement and medicine you take, including any creatine and pain relievers like ibuprofen or naproxen, plus any recent hard workout. The NIH says those pain relievers can damage your kidneys, especially in people with kidney disease, diabetes, or high blood pressure. You may be told to skip meat before the recheck. Drink normally, since the NKF says too much water isn't good either. Don't stop any medicine unless your doctor tells you to. If it does turn out to be your kidneys, the NIH calls blood pressure control the most important step you can take to treat kidney disease. No supplement, including the one I take, is a treatment for a high creatinine result.

The one I take is the red bag in the middle of the photo at the top, and it's the only one without "kidney" in its name. A lot of people head to the supplement aisle after a flagged result, so I read the back of all six. Four of the other five contain uva ursi, astragalus or both, herbs the NKF lists as high-risk for people with kidney disease. Three are sold as a cleanse or detox. One is freeze-dried beef kidney, at six capsules a day. And a cleanse from one of the best-known vitamin brands in America tells you, on its own label, not to take it daily for more than a month.

If you and your doctor decide a supplement makes sense, flip it over and check these three things first. It takes about 30 seconds.