Black or very dark urine is not normal and usually signals that something specific is going on, whether it’s a medication you’re taking, something you ate, severe dehydration, or a medical condition that needs attention. The cause ranges from completely harmless to potentially serious, so identifying the trigger matters.
Medications That Turn Urine Black
The most common reason for strikingly dark urine is a medication side effect. Several widely prescribed drugs can turn urine dark brown or black as your body processes and excretes them. This is a known, expected reaction and not a sign of kidney damage on its own.
Medications that commonly darken urine include:
- Certain antibiotics, particularly metronidazole (often prescribed for bacterial and parasitic infections) and nitrofurantoin (used for urinary tract infections)
- Laxatives containing senna, a plant-based ingredient found in many over-the-counter constipation remedies
- Muscle relaxants like methocarbamol
- Anti-seizure medications like phenytoin
- Antimalarial drugs such as chloroquine and primaquine
- Cholesterol-lowering statins
If you recently started any of these, your dark urine likely has a straightforward explanation. The color change typically resolves once you stop taking the medication.
Foods and Supplements
Eating large amounts of fava beans, rhubarb, or aloe can produce dark brown urine that may look nearly black, especially if you’re also somewhat dehydrated. Blackberries and beets can push urine toward a deep reddish-brown that might be mistaken for black in dim bathroom lighting. Iron supplements are another well-known culprit, often darkening both urine and stool.
A simple test: think back over the past 24 to 48 hours. If you ate any of these foods, try drinking plenty of water and see if the color returns to normal within a day. If it does, food was the likely cause.
Severe Dehydration
When you’re significantly dehydrated, your kidneys conserve water by producing highly concentrated urine. This can make urine appear extremely dark amber, brown, or even close to black. If you’ve been sweating heavily, vomiting, having diarrhea, or simply not drinking enough fluids, dehydration is the first thing to rule out. Rehydrating over several hours should bring the color back to a pale or medium yellow.
Muscle Breakdown (Rhabdomyolysis)
When muscle tissue breaks down rapidly, a protein called myoglobin floods into the bloodstream and gets filtered through the kidneys. This produces urine that looks tea- or cola-colored, and in severe cases it can appear nearly black. The condition is called rhabdomyolysis, and it can happen after extreme exercise, crush injuries, heatstroke, or prolonged immobilization.
Other signs include severe muscle pain or weakness, swelling in the affected muscles, and feeling generally very unwell. This is a medical emergency because excess myoglobin can damage the kidneys. If your dark urine follows intense physical exertion or injury and you’re also experiencing muscle pain, you need medical evaluation quickly.
Alkaptonuria
A rare genetic condition called alkaptonuria causes the body to incompletely break down certain amino acids. The leftover substance, homogentisic acid, builds up and gets excreted in urine. Here’s the distinctive clue: your urine may look relatively normal when it first comes out, then gradually turns black after sitting in the toilet or in a container exposed to air. The oxidation process darkens it over minutes to hours.
Over time, alkaptonuria also causes a blue-black pigment to accumulate in cartilage, the whites of the eyes, the outer ears, and the skin of the hands. Earwax and sweat can also darken. People with this condition often develop joint problems in their 30s and 40s as pigment deposits damage cartilage. It’s present from birth, so parents sometimes notice the darkening in a baby’s diaper.
Melanuria From Metastatic Melanoma
In rare cases, black urine is caused by melanin or its chemical precursors being excreted by the kidneys. This happens when melanoma, a type of skin cancer, has spread to internal organs. As melanoma cells break down inside the body, they release pigment compounds into the bloodstream, which eventually appear in urine. This occurs in roughly 15% of people with advanced metastatic melanoma, particularly when the cancer involves internal organs.
This is not a first sign of skin cancer. It occurs at advanced stages of disease, almost always in someone already diagnosed with melanoma. Still, if you have a history of melanoma and notice your urine turning unusually dark, it’s worth reporting to your oncologist.
Liver and Bile Problems
Your liver produces bile, which contains a pigment called bilirubin. When the liver is injured or bile ducts are blocked, excess bilirubin can spill into the bloodstream and eventually into your urine, turning it very dark brown. Conditions like hepatitis, cirrhosis, or gallstones blocking the bile duct can all produce this effect. You’ll often notice other symptoms too: yellowing of the skin or eyes, pale or clay-colored stools, abdominal pain, nausea, or fatigue.
What to Do Next
Start with the simplest explanations. Check whether you’re taking any medications known to darken urine, think about what you’ve eaten recently, and consider whether you might be dehydrated. Drink plenty of water over the next several hours and see if the color improves.
Black urine that persists after rehydrating, that you can’t trace to a food or medication, or that comes with other symptoms like muscle pain, abdominal pain, yellowing skin, or fever warrants prompt medical evaluation. A basic urine test can quickly identify whether the dark color comes from blood, myoglobin, bilirubin, or other compounds, pointing your doctor toward the underlying cause. If you also notice your urine darkens only after it sits for a while, mention that specifically, as it helps distinguish alkaptonuria from other causes.