Urine Color and Its Significance

Normal urine is pale yellow or straw-yellow in color. Urine may have a variety of other colors, including dark yellow, orange, pink, red, green, blue, brown and even black. These rainbow hues may be caused by dehydration, ingested foods and drinks, supplements, medications, injuries and illnesses.

Urochrome was the first name for the yellow pigment in urine. However, many researchers now say that urobilin is responsible for urine's yellow color. Some scientists consider urochrome and urobilin to be the same chemical, while others believe that they are different substances and that both occur in urine. Urobilin is produced from the breakdown of hemoglobin, the red pigment which transports oxygen around the body in red blood cells. The hemoglobin is released when old red blood cells are destroyed.

Dehydration causes less water to enter the urine, so it appears dark yellow. Urine is usually darkest when we get up in the morning, since we’ve spent the night without drinking. Dark yellow urine during the day indicates that we’re not drinking enough water and is likely to appear if we’ve been sweating heavily without replenishing our body’s water content.

Vitamin B2, also called riboflavin, is yellow in color. If we eat more riboflavin than we need – which sometime happens when we take Vitamin B2 supplements – the excess riboflavin enters the urine and gives it a fluorescent yellow or neon yellow appearance.

Eating a lot of carrots can turn urine yellow or orange and can give the skin a yellow-orange color, a condition known as carotenemia. The pigment responsible for these color changes is beta-carotene. Vitamin C can also color urine dark yellow or orange. Warfarin (brand name Coumadin), an anticoagulant, is one medication that causes urine to appear orange. Rifampin, an antibiotic, has a similar effect.

Pink or red urine may be caused by eating beets, blackberries or rhubarb. Red urine can also be caused by blood in the urine. The urine may contain red blood cells or may contain hemoglobin released from damaged red blood cells or myoglobin, released from damaged muscle cells. Myoglobin is a red pigment that stores oxygen in muscle cells. Blood in the urine could indicate an injured kidney, urinary bladder or urinary tract. Lead or mercury poisoning can also produce red urine.

In females, the openings from the gastrointestinal tract, urinary tract and reproductive tract are close together, so sometimes medical tests are needed to discover where blood in the urine is coming from.

Urine can turn pink after taking laxatives containing a substance called phenolphthalein. Phenolphthalein turns pink when it’s in alkaline urine. Some countries have banned phenolphthalein in laxatives, since at high doses the chemical has been found to cause cancer in lab animals.

Eating a lot of asparagus can sometimes turn urine green, and may give the urine a distinct odor. An infection by a bacterium called Pseudomonas aeruginosa can cause urine to turn green or blue.

Several medications may cause blue urine. These include amitriptyline, an antidepressant, indomethacin (trade name Indocin), a non-steroidal anti-inflammatory drug, cimetidine (trade name Tagamet), a stomach acid reducer and promethazine (trade name Phenergan), an anti-nausea drug. Urised, which is used to treat urinary tract pain, contains a dye called methylene blue which colors the urine.

Metabolic disorders can produce blue urine. Indicanuria is a condition in which the body cannot absorb the amino acid tryptophan from the intestine. Intestinal bacteria break the tryptophan down into chemicals that are excreted in the urine and cause it to appear blue. In babies, the disorder is sometimes called “blue diaper syndrome.” Familial hypercalcemia, an inherited disorder in which the level of calcium in the body is elevated, can also cause blue diaper syndrome.

Eating lots of fava beans or aloe can result in brown urine. So can taking cascara and senna laxatives. Methyldopa (brand name Aldomet), a drug given to help high blood pressure, can cause urine to turn black when it mixes with bleach in the toilet bowl. The antibiotic metronidazole darkens urine.

People with porphyria may have red-purple or red-brown urine. Porphyrin is a chemical used to make the heme (iron-containing) part of the hemoglobin molecule. If the body can’t make enough heme, excess porphyrin is excreted in the urine, giving the urine its distinct color. The porphyrin also causes many other symptoms in addition to colored urine. There are several types of porphyria. Some types affect the skin, causing blisters, swelling and itching when the skin is exposed to sunlight. Other forms affect the internal organs, nervous system and brain, causing symptoms such as pain, cramping, vomiting, numbness, paralysis, personality changes and mental disorders. King George III of Britain, who was known as the “mad” king, exhibited periods of body pain, paralysis and insanity. His doctors recorded the fact that he had dark red urine. Today’s researchers believe that King George probably suffered from porphyria.

Alkaptonuria (also spelled alcaptonuria) is an inherited condition in which urine becomes brown-black when it is exposed to air. In this disorder a person cannot completely break down two amino acids called phenylalanine and tyrosine. As a result a substance called homogentisic acid collects in the body, and is deposited in the urine, causing the urine to appear black when the acid reacts with air.

Some liver or kidney diseases can also produce brown urine.

The most common cause of cloudy urine is the presence of phosphate crystals in the urine. These crystals can appear after eating or drinking high-phosphate foods, such as milk. The phosphate crystals will disappear if a small quantity of vinegar is added to the urine.

Cloudy urine may sometimes be a sign of a urinary tract infection, which causes white blood cells to collect in the urine. White blood cells fight invading bacteria and viruses. The urinary tract infection may be accompanied by other symptoms, such as a frequent need to urinate and a burning sensation during urination.

A disorder called proteinuria can produce cloudy urine. In this condition protein builds up in the urine. Proteinuria is sometimes temporary and disappears without treatment, but it may indicate kidney damage. It can also be a symptom of certain diseases, such as diabetes and hypertension (high blood pressure). Proteinuria may develop in pregnant women who are suffering from preeclampsia.

Urine that looks like pure water, with no yellow color, may mean that a person is well hydrated or even over–hydrated. Drinking too much water can be dangerous, since it dilutes essential electrolytes inside the body.

Large amounts of colorless urine may be a symptom of diabetes insipidus, which is not the same condition as diabetes mellitus. In diabetes mellitus a person doesn’t make enough insulin, or their cells don’t respond to insulin properly. Insulin is a hormone made by the pancreas that increases the permeability of cells to glucose, the sugar that travels in blood. Diabetes mellitus is therefore sometimes called “sugar diabetes.” In diabetes insipidus, the body doesn’t produce enough antidiuretic hormone, which is also called vasopressin, or doesn’t respond to the hormone properly. Vasopressin stimulates the kidneys to send water back into the tissues and bloodstream so that it is not excreted in the urine. Without the hormone, too much urine is produced, and the person is constantly thirsty. Diabetes insipidus is sometimes called “water diabetes.”

Colored urine may indicate a medical problem or may be the result of ingesting certain foods, drinks, medications or multivitamins containing pigments or added dyes. Diagnostic dyes used in medical tests and medications can also color urine. It’s a good idea to check the information sheet that accompanies a prescribed medication or medical treatment so that you won’t be surprised by colored urine if this is one of the side effects. Unless a change in urine color can be related to diet or a medical treatment and quickly disappears once the food or treatment is stopped, a doctor’s advice should be sought for abnormal urine color.