Wondering what the colour of your urine means? If we pay any attention at all when we have a wee, we usually expect to see urine of various shades of yellow. It’s easy to understand why suddenly passing green, yellow or even blue urine might be alarming.
Dr Juliet McGrattan explores why urine might turn all the colours of the rainbow, and what it indicates about our underlying health.
What is urine?
Producing urine is one of the mechanisms our body uses to get rid of waste. The kidneys remove toxins and waste products from circulating blood and then dissolve them in water to create urine.
Urine travels from the kidneys along tubes called the ureters and into the bladder where it is stored, ready to be expelled when the ‘need to pee’ strikes. Urine is made up of around 90 to 95 per cent water.
The remainder consists of:
- Urea – formed from the breakdown of proteins
- Creatinine – from the breakdown of muscle
- Urobilin – from the breakdown of red blood cells.
Why is urine yellow?
The yellow colour of urine comes largely from the presence of urobilin, also known as urochrome. Urobilin, which is yellow, is produced as the body breaks down old red blood cells that are no longer needed.
How pale or dark yellow your urine is, is determined by how hydrated you are. Lots of water in the urine will make it appear lighter in colour and conversely, inadequate amounts will mean it’s more concentrated and darker.
A healthy urine is said to be a pale straw colour and we should drink enough water each day to maintain this. Urine is always darker in the mornings as it becomes more concentrated overnight when we sleep.
Unusual urine colours and what they mean
Sometimes urine changes colour and it can take you by surprise as well as trigger concerns about what might have caused it.
Because urine is clearing waste from the blood which has circulated right around the body, a change in urine colour can indicate a problem in various organs and systems.
Here are a variety of colours you might see and what they could indicate:
Red or pink urine
There are numerous causes of red or pink urine from something you have eaten through to infections and cancers. If you notice red urine without an obvious cause, then you should always see your nurse or doctor.
Here are some of the potential causes of red or pink urine:
• Red foodstuffs, such as beetroot or rhubarb which colour the urine
• Urine infection, where blood has leaked from blood vessels in the bladder or kidneys
• Kidney or bladder stones which scrape the delicate lining of the bladder, ureters or kidneys as they try to pass through the system
• Prostate infection or inflammation (in men)
• Menstruation – even a small drop of period blood can colour urine a pink or red colour
• Endometriosis – when tissue which lines the uterus has also grown in the bladder
• Strenuous exercise can sometimes cause blood loss from the bladder lining.
Brown urine may simply mean significant dehydration but there are other causes too:
• Foodstuffs, including rhubarb, fava beans, blackberries and aloe
• Dehydration can darken urine; this may be due to excessive fluid loss from sweating during exercise or with a fever or from inadequate fluid intake.
• Medications including the antibiotic metronidazole, antimalarials and some laxatives.
• Rhabdomyolysis – muscle breakdown due to excessive exercise, dehydration and trauma to muscles. It can also be caused by some illicit drugs, seizures and inherited medical conditions.
• Porphyria, a rare metabolic disorder which can cause a rusty-brown coloured urine as large numbers of porphyrins are excreted in and stain the urine.
• Old or ‘stale’ blood has a browner colour than fresh blood and can result from any of the causes of red urine listed above.
Again, orange urine can indicate that you need to drink more fluid or you’ve eaten something orange but it may be due to other more serious problems:
• Foodstuffs, including carrots
• Dehydration can cause urine to look orange
• Liver problems. When there is a build-up of excess bilirubin from the liver, the skin can turn a yellow colour (jaundice) and urine can turn a deep orange
Green is a more unusual and more startling colour for urine. It’s usually temporary and due to a simple reason but it can be linked to infections:
• Foodstuffs, such as asparagus or foods with green dyes
• Dyes given during medical tests, for example kidney investigations
• Medications, including some used during anaesthesia, for example propofol
• Urine infection by the bacteria pseudomonas can produce a green tinged urine
Urine always looks yellow but if it suddenly appears a very bright neon colour, then it may be due to consuming B vitamin supplements, particularly vitamin B12. B vitamins are water soluble so you ‘pee out’ any excess that your body hasn’t used.
Urine can be a very pale, almost white colour if you have drunk large quantities of water and the urine is very diluted. Cloudy urine can also appear a milky white and this might happen due to:
• Urine infection
A striking purple urine can occur with a rare condition called Purple Urine Bag Syndrome (PUBS). This usually affects people with a long term urinary catheter and a urine infection. The combination can result in deep purple urine.
Blue is an uncommon colour for urine because when blue pigment mixes with the yellow of urine, green is produced. However, blue urine might develop from:
• Foodstuffs with blue dyes
• Blue diaper syndrome, an extremely rare, inherited disease where there are errors in metabolism leading to high levels of calcium in the blood and sometimes blue stained urine. It’s usually detected in children.
• Urine infection with the bacteria pseudomonas.
If you have any concerns about the colour of your urine and there is no obvious cause for the colour change, then you should see your nurse or doctor. It’s helpful to take a freshly collected sample of urine in a sterilised container with you to your appointment.
Last updated: 26-08-2020
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