Why is my urine bright yellow? Colors, changes, and causes

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 colors of urine and why they change. If bright yellow means neon yellow, this has a specific cause.

Why is urine yellow?

A doctor holds a urine sample in a test tube
If anyone has concerns about urine, it is recommended that they visit a doctor.

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 color signals too much intake of vitamin B, although this is harmless.

What is the normal color for urine?

Urine color is normally pale yellow, but the depth of yellowness can vary healthily.

The yellow color 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 color?

The yellow color 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 color.

Urine color indicates hydration level

The yellow color in the urine has long been known to indicate the balance of fluids in the body. It has been only recently that urine color has been proven as a reliable way to monitor hydration during exercise.

People can look at the color 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 colors and their causes

A range of colors 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 color changes in the urine. It is best for people to take any concerns about urine to a doctor.

Orange urine

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.

Red urine

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.

Brown urine

A selection of different drugs in a box
Some drugs may turn the urine orange, brown, or green.

Medicines that alter the color 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.

Green urine

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 color 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 color 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 color. How it smells is one way it can change, as is how clear it is.

Cloudy urine

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.

A man bends down to pick up water on a running track
Urine color may be used to work out hydration levels.

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.

Urine odor

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

When to see a doctor about urine changes

Many of the changes to urine color are temporary or reversed when a certain product or food is no longer used. Most changes are harmless.

It is important to get medical help whenever dehydration is caused by illness, or the person is unable to take in fluids. This is especially important if there is no explanation for the dehydration or it is severe.

Dehydration can be dangerous for anyone, but especially vulnerable people like the very young or old.

A clear flag for getting medical help is red-colored urine. If there is any doubt about what is causing a change in the urine, people should see a doctor.

Some problems that change urine color are rare but serious. A tumor in the urinary tract is one example of a rare cause that needs an urgent diagnosis.

Seeing a doctor is also important if any changes last longer than 2 or 3 days. Further symptoms that cause any concern should also be looked at.