What colour should urine be?
In this article we will describe what colour should urine be, as part of 10 facts about urine (wee or pee).
1. So. What colour should urine be?
The yellow colour of urine comes from a pigment called urochrome, which is produced during the breakdown of haemoglobin.
Urine is usually pale straw or transparent yellow, but its colour can change depending on what you eat and drink.
For example, the colour of urine can indicate hydration levels. Pale yellow suggests proper hydration, while dark yellow/amber/brown can indicate dehydration.
Red or pink urine can be caused by blood or eating certain foods like beetroots; and cloudy urine can suggest an infection.
Blood in the urine can be macroscopic (that you can see) or microscopic (that you cannot).
The former should always be reported to a doctor and investigated (it can indicate a cancer of the kidney, ureter or bladder; or prostate in a man). Some cases of the latter should be investigated.
Although 10% of the normal population have microscopic haematuria – i.e in most people, it is not a disease.
Let’s go back.
2. What is urine?
Urine is about 95% water. It is 2.5% urea, and the remaining 2.5% is comprised of salts, hormones, and various waste products like creatinine and uric acid, which the body needs to eliminate. It also contains small amounts of DNA, RNA, and proteins.
3. Volume (urine and bladder)
- Urine. The average adult produces between 1.5-2.5 L of urine each day, depending on fluid intake
- Bladder. The full bladder is quite small (300 ml, i.e. a can of coke). When it’s empty, it’s about the size of a small pear.
4. Urination frequency
On average, people urinate about 7 (6-8) times a day (7 x 300 ml = 2.1 L). Increased frequency can be a sign of high fluid intake, caffeine or alcohol consumption, or underlying health conditions like diabetes or a urinary tract infection.
Passing urine too frequently is well known as a first presentation of diabetes. Have a blood glucose measured if this is happening to you.
5. pH Level
Urine is slightly acidic, with a normal pH range of about 4.5 to 8. The pH varies based on diet, hydration, and health conditions.
6. Odour
Urine normally has a slight odour, but it can change due to diet, medications, or health conditions. For instance, eating asparagus can give urine a distinctive smell due to the breakdown of certain sulphur compounds.
7. Sterility
Fresh urine is typically sterile, meaning it does not contain bacteria, viruses or any other micro-organism. In other words, it is not infected or infectious. However, it can become contaminated once it leaves the body, or become infected if the person has a urinary tract infection (UTI).
UTIs are not contagious, i.e. they cannot be passed from one person to another.
8. Diagnostic tool
Urine tests – like a urine dipstick, midstream specimen of urine (MSU, for a UTI), and urinary ACR (protein in urine) – are common diagnostic tools used in medicine (and by the police). They can detect conditions like diabetes, increased protein in the urine (can be a sign of chronic kidney disease, CKD), infections (UTIs), pregnancy or recreational drugs.
9. History of urine
- In ancient Rome, urine was used to clean clothes because of its ammonia content, acting as a natural cleaning agent
In this stall, laundry workers in ancient Rome cleaned clothes with a mix of urine and clay
- Ancient Roman spies – used urine as invisible ink to write secret messages that would appear when heated
- Urine fueled centuries of wars. Gunpowder comprises 75 percent potassium nitrate, a.k.a. saltpeter; 10 percent sulphur, and 15 percent charcoal. Until the mid-19th century, saltpeter was either imported from India or made locally from stale urine
- Medical uses. Urine has been used as an antiseptic for thousands of years. It was believed to help treat wounds and infections
- Cultural practices. In some cultures, urine has been used in traditional medicine for various treatments, although its effectiveness is often debated
- Ancient Egyptian pregnancy test. The first known DIY pregnancy test is described in the Berlin Papyrus from 1350 BCE: “Wheat and spelt: let the woman water them daily with her urine like dates and like sh’at seeds in two bags. If they both grow, she will bear; if the wheat grows, it will be a boy; if the spelt grows, it will be a girl. If neither grows, she will not bear,” it advises, according to one translation.Modern scientists put this to the test in 1963 and found that it correctly identified 70 percent of the pregnancies in the study.
10. Other facts
- Urine is a natural fertilizer. Due to its nutrient content, urine can serve as an effective natural fertilizer. It contains essential nutrients such as nitrogen, phosphorus, and potassium, which can support plant growth when diluted and applied to soil
- Chemical reactions. Urine can react with certain chemicals. For example, when exposed to bleach, urine can produce chlorine gas, which is toxic. This is why it is important to avoid mixing household cleaners with urine
- Astronauts recycle their urine into drinking water. As normal human urine is about 95 percent water, it presents a very appealing target for recycling; especially where potable water is scarce, like the International Space Station. On the ISS, the American crew derives its drinking water supply by recycling urine (and condensate from air)
- Medical uses. In certain medical scenarios, components derived from urine, such as urokinase and human chorionic gonadotropin (HCG), have been used for therapeutic purposes; showcasing the potential medical applications of urine-derived substances
- Mammals empty their bladders on average for 21 seconds
.. despite a difference in bladder volume from 0.15 ml (mouse) and 300 ml (human), to 18 L (elephant) and 300 L (blue whale). This is called the Law of Urination.
[“It’s amazing what you can learn here about elephants peeing”. MyHSN Ed]
Summary
We have described what colour should urine be, and 9 other facts about urine. We hope it has been interesting.
Other resources
Review article: Cortes, 2023
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