Changes in urine – When to see the doctor

Urine is simply excess water and waste products that your kidneys filter from your blood. Its color usually ranges from pale yellow to deep amber, depending on its concentration — the proportion of waste products to water. That, in turn, depends partly on how much fluid you consume.

For the most part, we pay little attention to urine, unless it looks or smells unusual. A surprising number of things can affect the color and odor of your urine. The most common ones are harmless and temporary, including foods, vitamins, and certain medications. But sometimes changes in urine signal a medical problem, which may range from relatively benign (a urinary tract infection) to serious (kidney or bladder cancer). Here are some suggestions on when you can relax and when you should consult your clinician.

Vegetables, fruits, and vitamins

Beets, blackberries, and rhubarb can temporarily turn urine pink or red, which can be alarming, because it may be mistaken for blood. The pigment that gives beets their deep magenta color is stable only at certain levels of stomach acidity and is usually too faint to show up in most people's urine. The phenomenon — dubbed "beeturia" — occurs in only about 10% to 14% of the population. Even if you're in that select group, eating beets won't always have a visible effect, because the acidity of your stomach (and therefore your urine) depends on when you ate and what else you ate. Rhubarb can also turn urine dark brown or tea-colored, as can fava beans and aloe. Carrots, carrot juice, and vitamin C can color urine orange, and B vitamins can turn it a fluorescent yellow-green.

Asparagus sometimes gives urine a greenish tinge and a distinctive smell. Why this occurs is a matter for speculation. Some blame it on the sulfur-containing fertilizers used on asparagus plants (there is no record of the vegetable changing urine odor before such fertilizers were introduced). Others suggest that only people who carry a particular gene break down the sulfur-containing proteins in asparagus that release the odor. Still another view is that the smell of everyone's urine undergoes a change, but only some of us notice it. The current consensus seems to be that some of us produce smelly urine after eating asparagus, and some of us do not, while some can detect the odor and some cannot.

Medications and medical problems

Various prescription and over-the-counter medications can change the look of your urine. So can certain medical conditions, most commonly urinary tract infections (UTIs), which affect about half of all women at least once during their lives. The mucus and white blood cells associated with UTIs can turn urine cloudy and cause an unpleasant odor. Symptoms also include a frequent and urgent need to urinate, burning pain with urination, and abdominal pain. Contact your clinician if you experience these symptoms, which usually disappear quickly after you start oral antibiotics.

UTIs can also cause blood in the urine (hematuria). If the amount is very small, the urine appears normal, and the blood is visible only under a microscope. Larger amounts can cause urine to appear pinkish, red, or cola-colored.

Another possible cause of hematuria is kidney stones — hard, crystalline masses ranging in size from a grain of sand to a pearl that form within the urinary tract or kidney. A stone may cause hematuria if it irritates the ureter (the tube that carries urine from the kidney to the bladder). Kidney stones can also cause extreme pain in your back or side, and fever, chills, and vomiting, for which you should seek immediate medical attention. But most stones will pass out of the body without medical intervention.

Hematuria can also result from an injury to the upper or lower urinary tract (for example, in a car accident or bad fall). Strenuous exercise (especially running) can sometimes cause hematuria because the repeated jarring damages the bladder. Less common sources of hematuria are bladder cancer and kidney cancer or other kidney disease — so be sure to check with your doctor if your urine appears reddish for no apparent reason.