Normal urine should be a pale yellow color. It should be clear, without cloudiness or particle deposits.
“Why is my urine bright yellow?” is a question that can be answered if the meaning of bright yellow is clear.
This page will explain the full range of possible colours of urine and why they change. If bright yellow means neon yellow, this has a specific cause.
Why does urine turn bright yellow?
To answer the question of bright yellow urine color, it may help to cover what it means when urine is really fluorescent bright.
Neon yellow urine colour signals too much intake of vitamin B, although this is harmless.
What is the normal colour for urine?
Urine colour is normally pale yellow, but the depth of yellowness can vary healthily.
The yellow colour gets darker as the concentration of the urine gets higher. Concentration means the proportion of waste products to water in the urine.
The proportion of waste products to water increases and the urine darkens, as less fluid is taken in. This also happens if more fluid is lost by other means such as sweating.
What gives urine its healthy yellow colour?
The yellow colour in normal urine comes from a substance known as urochrome. Urochrome is also known as urobilin and is the result of hemoglobin breakdown.
Hemoglobin is the protein in red blood cells that enables oxygen to be taken around the body. Red blood cells are renewed in their millions every day, so old ones must be broken down. The urochrome by-product of this process ends up in the urine as a yellow colour.
Urine colour indicates hydration level
The yellow colour in the urine has long been known to indicate the balance of fluids in the body. It has been only recently that urine colour has been proven as a reliable way to monitor hydration during exercise.
People can look at the colour of their urine and use it to work out if they have taken in enough fluids or not. Darker shades of yellow suggest that the person may be dehydrated and need water.
Abnormal urine colours and their causes
A range of colours can appear in the urine, and some signal a medical problem. Many of the possible causes are below, but it is not a complete list. There may be other causes of colour changes in the urine. It is best for people to take any concerns about urine to a doctor.
Orange urine can be caused by drugs. Examples include the antibiotic rifampicin and the pain-relief drug phenazopyridine, used for urinary bladder pain. Some laxatives and chemotherapy agents can also color the urine orange.
Diet factors behind orange urine include a high intake of carrots, because of a substance called carotene that these vegetables contain. Vitamin C, blackberries, beetroot, or rhubarb can also have an effect.
A red color in the urine has a number of causes.
Blood in the urine is one cause, and a reason to see a doctor. Blood in the urine is known as hematuria.
A blood-related condition known as hemoglobinuria can also cause red urine, as can myoglobinuria, which is to do with muscles.
Harmless causes of redness in the urine include beetroot or blackberries in the diet.
Medicines that alter the colour of urine to brown include:
- Antipsychotic drugs such as chlorpromazine (Thorazine) and thioridazine (Mellaril)
- Antibiotics such as metronidazole (e.g. Flagyl) and nitrofurantoin (e.g. Furadantin)
- An epilepsy drug called phenytoin (e.g. Dilantin)
- Sennoside laxatives (Senna-Lax, Senokot)
Deep purple urine
A condition called porphyria causes urine to appear deep purple. Porphyria is a rare metabolic disorder.
The urine can turn green because of the following:
- Drugs and other compounds containing phenol, such as promethazine used for allergy and nausea, and propofol, a drug used in anesthetics
- Other drugs, including the antidepressant amitriptyline, cimetidine, which reduces stomach acid, and the painkiller indomethacin
- Dyes, including indigo-blue, indigo carmine used in kidney tests, carbolic acid, and flavin derivatives
- Biliverdin, a bile pigment
- Infection with Pseudomonas bacteria
Methylene blue, a dye that has also been used as a drug, can produce a blue-green colour to the urine.
Medical journals often publish case reports. These tend to describe unusual cases seen by doctors. One published in 1999 in the journal Nephrology, Dialysis, Transplantation was entitled, A case of ‘green urine.’
The patient’s green urine was thought to have been caused by a bowel disease called ulcerative colitis. The authors wrote that the illness meant a food colour that cannot usually be absorbed was absorbed across the patient’s diseased gut lining.
Other signs to look out for in the urine
Urine can indicate changes in the body in other ways aside from colour. How it smells is one way it can change, as is how clear it is.
Cloudy urine can signal a number of possible problems. For women, it could be due to vaginal discharge. Other changes that may cause cloudiness include:
- Dehydration can make urine foamy
- Urinary bladder infections and lower urinary tract infections
- Kidney disease, including kidney stones
White or milky-looking urine can also be caused by infection. Another cause of this is too much of minerals such as calcium, or too much protein in the urine.
Kidney problems and excess protein can also make the urine foamy. Temporary foaminess is usually a result of an unsteady urine flow. If cloudiness in the urine lasts for more than a few days, a doctor should investigate the cause.
The smell of urine can change. Some changes are harmless, while others are a sign of disease:
- Eating a lot of asparagus can make the urine smell like rotting cabbage
- Urinary tract infections can cause the urine to have a foul smell
- Urine that smells sweet could be a sign of diabetes