Doctor Warns To Avoid This Common Supplement Before Blood Tests

It can throw your readings way off, Dr. Raj says.
Carol Yepes via Getty Images

Dr. Karan Raj, a doctor who’s become TikTok-famous for sharing his medical know-how, recently shared that creatine ― a compound mostly found in the body’s muscles and brain ― can affect your kidney function readings if taken in its synthetic supplement form.

In a recent video, the doctor said, “I recently had some routine blood tests done ― and it showed that something was wrong with my kidneys.”

Here’s how he discovered his fave supplement was to blame:

It’s all about creatinine

Creatinine is a waste product made by your body. And if your levels are high, it suggests your body isn’t flushing the substance out properly ― meaning you may have issues with your kidney function.

Dr. Raj noticed that, in his test results, his creatinine levels were high ― “not good,” he said. And his eGFR (estimated glomerular filtration rate), which shows how well your kidneys are filtering waste out, was in the “low to normal” range.

As in, it was “lower than you’d expect for the 33-year-old male with no medical conditions.”

So, after doing some research, the doctor found that the problem was coming from his supplement tub.

“You see, creatinine is a breakdown product of creatine. The more creatine you have, like a supplement, means it’s more likely you’ll have higher creatinine,” he says.

The eGFR, or kidney function score, is based on the creatinine levels, he says. So, if the creatinine “is falsely elevated, it can give you a wrong kidney function calculation.”

Huh! So how long should I wait after taking creatinine until my readings are accurate?

Well, you could tell your doctor about your supplement use to account for any changes. But if you want a reading unaffected by creatine interference, you might have to wait longer than you’d think.

“I stopped creatine supplements for a week and got repeat blood tests ― the creatinine was now normal,” the doctor said.

But “if you supplement creatine, it can stay in your system for six to eight weeks,” he warned. He’ll be returning for another round of tests after a couple of months.

“Creatine supplementation does not harm the kidneys,” he adds, in the same way that the fluorescent yellow urine you get from taking B2 supplements doesn’t mean your bladder has actually been harmed.

But, like with the neon pee, it can give an alarming-looking result ― except that creatine causes panic from your blood tests rather than your toilet bowl.

It can “contribute as a false indicator of kidney injury,” the doctor said. So “make sure you let your doctor know if you supplement with creatine.”