Urine Color and Its Meaning in Health and in Disease
An Interesting and Important Liquid
Peeing multiple times a day is such a routine part of our lives that most of us never think much about it. Urination is actually a vital function of our body. It plays a major role in maintaining proper hydration, helps to regulate pH, and gets rid of waste substances. A variation in the usual color of urine (or pee) requires attention because it may indicate a health problem.
Urine is normally pale yellow or straw-yellow in color. It may have a variety of other colors, however, 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.
If your urine has an unusual color, there's a good chance that the change is caused by a harmless factor. Some detective work is necessary, however, to pinpoint the cause of the change. If there is no apparent cause or if the strange appearance continues, a doctor's advice should be sought.
Urine is produced by the kidneys from blood plasma, stored in the urinary bladder, and then excreted out of the body when the bladder is full. It contains water, salts, and wastes produced by cell activity.
Normal Urine Color
Urochrome was the first name for the yellow pigment in urine. This chemical is now known as urobilin. A few sources consider urochrome and urobilin to be different molecules, however.
Urobilin is produced from the breakdown of hemoglobin, a pigment inside our red blood cells. Hemoglobin transports inhaled oxygen around the body and releases it to tissue cells. The hemoglobin is broken down when old red blood cells are destroyed, which happens regularly. The cells live for only about 120 days.
Dehydration causes less water to enter the urine. The pee appears dark yellow because the urobilin is concentrated. 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 suggests that we’re not drinking enough water. It may appear if we’ve been sweating heavily without replenishing our body’s water content. It's important to keep in mind the quote from the nephrologist below, however. A nephrologist is a doctor who specializes in kidney function.
I never advise people to examine their urine color for hydration and never would recommend hydrating based on urine color. Instead, ‘drink to thirst.'— Dena Rifkin MD, UC San Diego Health
A Urine Color Chart
The website of Carleton University in Ottawa, Canada, provides a urine color chart to check for hydration, although based on what the doctor quoted above says it may have limited value. (A link to the chart is given in the "References" section below.) The chart can be printed, but if you do this check that your printer produces colors that match the ones on the screen. The colors on the monitor screen may not be accurate, however.
Another problem with analyzing urine appearance is that the lighting in different rooms can affect the color, as can the exposure of a photograph. The recent ingestion of foods, drinks, vitamins, medications, or dyes that color the urine is yet another reason why a chart may be inaccurate.
There are many factors that can color urine, including foods, medications, and certain diseases. The information given below is for general interest only. A doctor should be consulted if urine has an unusual color with no obvious explanation.
Fluorescent Yellow or Orange Pee
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 also give the skin a yellow-orange color, a condition known as carotenemia. The pigment responsible for these changes is beta-carotene. Vitamin C can also color urine dark yellow or orange. Warfarin (brand name Coumadin) is an anticoagulant and is one medication that causes pee to appear orange. Rifampin, an antibiotic, has a similar effect.
There are other drugs that can color urine besides the ones that I mention in this article. The product brochure of a drug, your pharmacist, or your doctor can tell you about a possible color change.
Pink or Red Urine
Pink or occasionally red urine may be caused by eating beets, blackberries, or rhubarb. Pee can also 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.
Red urine may develop due to unusual bleeding that is not part of menstruation. Urine may sometimes contain red blood cells or hemoglobin released from damaged red blood cells. It may also contain myoglobin. Myoglobin is a red pigment that stores oxygen in muscles. Damaged muscle cells may release myoglobin, turning pee red. Blood in the urine could indicate an injured kidney, urinary bladder, or urinary tract.
Red urine is not necessarily caused by blood. Phenazopyridine (trade name Pyridium) is a medication that acts as an anesthetic in the urinary tract. It's prescribed for urinary tract infections and injuries and after medical tests or surgery on the tract. One of the medication's side effects is the production of an orange-red urine. Use of a senna laxative can sometimes produce red pee. The disease known as porphyria can also produce a reddish urine, as described below.
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.
Green or Blue Pee
Eating a lot of asparagus can sometimes turn urine green and may also give the urine a distinct odor. An infection by a bacterium called Pseudomonas aeruginosa can cause pee to turn green or blue.
Several medications may cause blue urine. These include:
- amitriptyline, an antidepressant
- indomethacin (trade name Indocin), a nonsteroidal anti-inflammatory drug
- cimetidine (trade name Tagamet), a stomach acid reducer
- promethazine (trade name Phenergan), an anti-nausea drug
- urised, a pain reliever for urinary tract problems; contains a dye called methylene blue, which stains pee
Metabolic disorders can also produce blue urine. Indicanuria is a condition in which the body is unable to 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.” The condition is sometimes accompanied by familial hypercalcemia, a condition in which the blood calcium level is too high.
Brown or Black Urine
Eating lots of aloe or fava beans (also called broad beans) can result in brown urine. Taking a cascara laxative can produce the same effect. A senna laxative can cause a red, red-brown, or brown urine. Methyldopa (brand name Aldomet), a drug given to help high blood pressure, can cause urine to turn black when the liquid mixes with bleach in the toilet bowl. The antibiotic metronidazole darkens urine.
Alkaptonuria (also spelled alcaptonuria) is an inherited condition in which urine becomes brown-black when it's 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. The urine appears black when the acid reacts with air.
Liver diseases such as hepatitis and cirrhosis, kidney disease. and kidney stones can all produce dark brown urine. Dark urine is also a symptom of some types of cancer.
The terms porphyrin and porphyria are derived from the Greek word porphyrus, meaning purple.— American Porphyria Foundation
The Biology of Porphyria
People with porphyria may have red-brown or red-purple urine. The illness develops when someone lacks a specific enzyme involved in the production of heme, the red, iron-containing part of the hemoglobin molecule. Heme belongs to the group of chemicals known as porphyrins, which are often intensely colored.
Heme is produced in a series of steps involving molecues known as heme precursors. Each step is controlled by a specific enzyme and makes a new precursor molecule. The molecule is then converted to a different precursor in the next step.
In people with porphyria, one of the enzymes involved in heme production is missing. This means that a specific precursor can’t be changed into the next one in the chain or into heme, the end product of the process. Precursor molecules build up in the body and may reach a toxic level. They collect in the skin, the organs, the feces, and the urine. The molecules are colorless, but when those in urine are exposed to light they are converted into colored porphyrins.
Acute Intermittent Porphyria (AIP)
Types of Porphyria
There are at least eight 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 or red-purple urine on several occasions. Today’s researchers believe that King George probably suffered from a form of porphyria.
Porphyria is caused by a genetic problem. Sometimes the disorder is inactive and only becomes active when a person is exposed to a stress of some kind. Doctors today have several ways to treat the disorder.
The most common cause of cloudy urine is the presence of phosphate crystals. These crystals may appear after eating or drinking high-phosphate foods, such as milk. They 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 also produce cloudy urine. In this condition protein builds up in pee. 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. This is a condition in which a woman develops high blood pressure and a high protein level in her urine during pregnancy.
Diabetes insipidus is a condition caused by a problem involving antidiuretic hormone or ADH. It's not the same condition as diabetes mellitus, which is caused by a problem involving insulin.
Urine that looks like pure water, with no yellow color, may indicate 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 (which is commonly broken down into type 1, type 2, and gestational diabetes), 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 cell membranes to glucose, the sugar that travels in blood. The hormone allows glucose to leave the blood and enter the cells, where it's used as an energy source. Diabetes mellitus is sometimes called sugar diabetes, since glucose collects in the blood of an untreated diabetic.
In diabetes insipidus, the body doesn’t produce enough antidiuretic hormone (also known as ADH and vasopressin), or the kidneys don't respond to the hormone properly. ADH is made by the hypothalamus in the brain and stored in the posterior pituitary gland until it's needed. The hormone stimulates the kidneys to send water back into the tissues and bloodstream so that it isn't excreted in the urine. Without ADH, too much urine is produced and the person is constantly thirsty. Diabetes insipidus is sometimes called water diabetes.
A Nurse Describes Diabetes Insipidus Symptoms
Although diabetes insipidus and diabetes mellitus are unrelated diseases, they both have increased thirst and urination as symptoms. These symptoms should always be investigated by a doctor.
Investigating Urine With an Abnormal Color
Urine with an abnormal color 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.
It's important to discover why urine has changed color. Unless a change in appearance can be related to diet or a medical treatment and quickly disappears once the food or treatment is stopped, a doctor should be consulted.
Questions & Answers
What does foul smelling urine indicate?
Urine may smell bad simply because we're dehydrated or because it's more concentrated when we wake up in the morning. Certain medications or foods—such as asparagus—can also make urine smell bad. The odor may be due to a health problem such as a urinary tract infection, however. A genetic problem can also produce the smell. If the bad odor doesn't disappear soon, a doctor's advice should be sought.
© 2010 Linda Crampton