Metallic-smelling urine usually comes from something you consumed, whether that’s a supplement, a medication, or certain foods. Less commonly, it can signal dehydration, a urinary tract infection, or a metabolic issue like uncontrolled blood sugar. In most cases, the cause is harmless and temporary.
Vitamins and Supplements
Iron supplements are one of the most common culprits behind a metallic urine smell. When your body absorbs more iron than it needs, the excess is filtered out through your kidneys, and it can give urine a distinctly metallic or coppery scent. Multivitamins that contain iron have the same effect. If you recently started a new supplement and noticed the change, that’s very likely your answer.
B vitamins can also change how your urine smells and looks. Extra vitamin B6 can give urine a strong, unusual odor, while excess B1 can produce a fishy smell. B vitamins are also responsible for turning urine a bright greenish-yellow, which can be alarming if you’re not expecting it. Prenatal vitamins, which combine iron with B vitamins and folic acid, are especially likely to change your urine’s smell and color at the same time.
Dehydration Concentrates Everything
When you’re not drinking enough water, your kidneys produce less urine with a higher concentration of waste products. Compounds that normally pass through at low, undetectable levels become concentrated enough to notice. Mild dehydration can make urine smell stronger in general, and if there’s even a small amount of iron or other minerals being excreted, the metallic quality becomes much more obvious. Dark yellow urine paired with an unusual smell is a strong sign you simply need more fluids. Drinking enough water to keep your urine a pale straw color usually resolves the issue within hours.
Medications That Alter Urine
Several prescription drugs can change how your urine smells or looks. Metronidazole, an antibiotic commonly prescribed for bacterial infections, is known to cause a metallic taste in the mouth and can also darken urine to a brown or reddish-brown color. Nitrofurantoin, another antibiotic used for urinary tract infections, can do the same. These changes are listed as known side effects and are not dangerous on their own, though they can be unsettling if you weren’t warned to expect them.
Some chemotherapy drugs, seizure medications, and even high doses of acetaminophen can also alter urine odor. If the metallic smell appeared shortly after starting a new medication, the timing is probably not a coincidence.
Urinary Tract Infections
Bacterial infections in the bladder or urinary tract produce foul-smelling urine, and some people describe the odor as metallic rather than simply “bad.” A UTI usually comes with other symptoms: burning during urination, a frequent urge to go, cloudy or pinkish urine, or pelvic pressure. If you’re experiencing any of those alongside the unusual smell, a simple urine test can confirm whether bacteria are present.
Blood in the Urine
Blood contains iron, and even a tiny amount of blood in your urine can produce a metallic smell. This is called hematuria, and it’s not always visible to the naked eye. Microscopic amounts of blood can change the odor without turning the urine pink or red. Causes range from harmless (intense exercise, menstrual contamination of a urine sample) to things worth checking out (kidney stones, bladder infections, or issues with the urinary tract). If you notice a persistent metallic smell with no dietary explanation, a urinalysis can detect hidden blood.
Ketones and Blood Sugar
When the body doesn’t have enough insulin to use glucose for energy, it starts breaking down fat instead. That fat breakdown produces acids called ketones, which build up in the blood and spill into the urine. People with poorly controlled diabetes are most at risk, and ketone-heavy urine often has a sharp, chemical, or metallic quality. Some describe it as smelling like nail polish remover.
Ketones can also appear in your urine during strict low-carb or ketogenic diets, prolonged fasting, or after intense exercise. In the context of diabetes, a strong chemical or metallic urine odor combined with excessive thirst, frequent urination, nausea, or confusion could indicate diabetic ketoacidosis, a serious condition that needs immediate medical attention. Outside of diabetes, dietary ketones are generally harmless and resolve when you eat carbohydrates again.
Pregnancy and Heightened Smell
Sometimes the urine hasn’t changed at all. Your nose has. In early pregnancy, many people develop hyperosmia, a dramatically heightened sense of smell. Ammonia is naturally present in urine at low levels, and compounds you’d never normally detect can suddenly become noticeable. A faint metallic or chemical note that was always there may become impossible to ignore. Prenatal vitamins, which are high in iron, can compound the effect by genuinely changing the urine’s composition at the same time your sensitivity to odors is peaking.
What the Smell Is Telling You
A metallic urine smell that appeared after you started a new supplement, changed your diet, or aren’t drinking enough water is almost always benign. Try increasing your fluid intake and see if the smell fades over a day or two. If you’re taking iron or a multivitamin, the smell may simply persist for as long as you’re on that supplement.
The smell deserves a closer look if it lasts more than a few days without an obvious dietary cause, if it comes with pain or burning, if your urine looks cloudy, dark, or reddish, or if you have symptoms like unusual thirst, fatigue, or nausea. A basic urinalysis can check for blood, bacteria, ketones, and glucose all at once, and it’s one of the simplest tests in medicine.