Medications That Can Turn Your Pee Black

At the first sight of black pee in the toilet, your stomach might lurch, and your brain may start panicking thinking that something is seriously wrong. While healthy urine normally appears clear or a light yellow color, black pee is about as far from clear as one can get. Sometimes, dark pee may be the result of a severe muscle injury from overtraining, which can cause our urine to resemble the color of a Coca-Cola, explains the Mayo Clinic. Other times, black pee may stem from a health condition. If you've ruled out the first two options, however, consider taking a look at your prescription medications.

Metronidazole, known by the brand name Flagyl, is one such drug that may cause a patient's urine to turn black, as outlined in a 2014 case report published in the Journal of Pharmacy Technology. The medication is used to treat certain parasitic and bacterial infections, predominantly those of the stomach, liver, vagina, and bloodstream (per Drugs.com). In the case report, a male in his early 50s with pre-existing health conditions had been treated with metronidazole for a Clostridium difficile (C. diff) infection. The patient subsequently presented with cola-colored urine, which cleared up after 34 hours of stopping the antibiotic treatment but returned upon re-administration of the drug. The researchers noted that no dangerous adverse outcomes were associated with the presence of black pee.

In a 2022 case report published in the World Journal of Clinical Case Reports and Case Series, researchers examined the case of a woman in her early 70s who presented with black urine among other symptoms. In order to determine the cause (which turned out to be a combination of rhabdomyolysis and type 2 diabetes), the researchers pointed out that they first had to rule out medications known to cause black pee, such as ferric preparations. Ferric preparations are iron supplements often used for the treatment of anemia, according to a 2014 study published in Advances in Hematology.

Another medication mentioned in the 2022 case report that the researchers stated they had to rule out was pyrogallol. Acting as an antipsoriatic and antiseptic, pyrogallol is a topical prescription medication used to alleviate certain skin conditions, including dermatitis and psoriasis (per Bayview Pharmacy). 

Phenol medications — sometimes used in the making of throat-numbing sprays, certain vaccines, or in the treatment of ingrown toenails (per Healthline) — were also accounted for in the case study. Experts at Medscape note that black urine can be a sign of phenol poisoning.

A type of muscle relaxant known as methocarbamol has also been associated with black pee as a side effect (per Medscape). With the brand name Robaxin, the drug slows down the nervous system and may be prescribed for short-term symptom relief if you suffer a muscle strain, sprain, or in cases of certain bone conditions (per Mayo Clinic, MedlinePlus). Patients should promptly check with their physician if they develop dark urine or black, tarry stools in association with methocarbamol use.

Although not commonly used nowadays, alpha-methyldopa is a high-blood-pressure drug that has also been linked with black urine (per StatPearls). The same is true of levodopa, a drug used to help reduce symptoms of Parkinson's disease, which may be prescribed off-label for intermittent restless leg syndrome or a condition known as periodic limb movement in sleep (per StatPearls). 

However, even non-prescription drugs can cause our urine to take on a darker shade; this includes laxative supplements containing senna leaves or cascara bark. Therefore, it's always best to consult with your doctor before starting any new medications or supplements and discuss any concerns you may have about urine discoloration.