Dark urine: causes, red flags and when to get it checked

The colour of urine reflects how concentrated it is. When you have not had enough to drink, or have lost fluid through sweating, vomiting or diarrhoea, urine becomes darker and stronger smelling. In that case it should lighten within a few hours of drinking properly. The NHS advice is to drink enough during the day so that your pee is a pale colour.

Dark urine that does not lighten with fluids, or that comes with other symptoms, is a different matter. The things to look for are yellow skin or eyes, pale stools, itching, pain in the tummy or side, burning or frequent passing of urine, a high temperature, or urine that looks brown, red or cola-coloured. Each of these changes the likely cause.

The NHS says dehydration means your body loses more fluid than you take in. Symptoms include thirst, headache, feeling light-headed or dizzy, dark yellow strong-smelling pee, peeing less often, tiredness and a dry mouth, lips and tongue. It is more likely if you have diabetes, have been sick or have diarrhoea, have been in the sun or heat, have drunk too much alcohol, sweat a lot after exercise, have a high temperature, take diuretics, or rely on others for drinks.

Treatment is to drink fluids, starting with small sips if you feel sick, and to avoid caffeinated drinks and alcohol. A pharmacist can recommend oral rehydration solutions if you are being sick or have diarrhoea. The NHS says to speak to a pharmacist about dark, smelly pee or peeing less than usual if you have diarrhoea and vomiting, particularly if you are an older person or have a weakened immune system.

Urgent advice applies if you feel unusually tired, dizzy on standing that does not go away, have a fast heart rate or breathing, or are peeing very little. The NHS says call 999 for signs of shock such as cold skin, confusion, difficulty breathing or being difficult to wake.

The NHS lists pain or burning on peeing, needing to pee more often, needing to pee suddenly, cloudy pee, blood in the pee, lower tummy or back pain, a high temperature and feeling tired or weak as symptoms of a urinary tract infection. It adds that pee may also be dark or smell, but that if this is your only symptom it might be because you have not been drinking enough water.

Blood in the urine can make it look pink, red or dark brown. The NHS says that if you think you have blood in your pee you need to get it checked, even if there is only a small amount or you are not sure it is blood, because it can be a sign of cancer and cancer may be easier to treat if found early. It lists beetroot and some medicines as things that can turn pee pink, red or brown, and says bleeding from the bottom or during a period may be mistaken for blood in the urine.

Kidney stones can cause severe pain in the sides, back or groin that comes and goes with nausea and blood in the pee, according to the NHS.

Bilirubin is the yellow pigment that builds up when bile cannot drain properly or the liver is not clearing it. The NHS says jaundice, with yellow skin or whites of the eyes, may come with itchy skin, darker pee and paler poo than usual, and lists alcohol-related liver disease, gallstones, hepatitis, pancreatitis and sickle cell disease among the causes. Yellowing of the skin may be less noticeable on brown or black skin but the whites of the eyes will look yellow.

Gallstones are common and often silent, but the NHS says a blockage can cause pain, and complications include jaundice with darker pee and paler poo. The NHS lists jaundice among the symptoms of pancreatic cancer alongside darker pee and paler poo, which is why dark urine with yellow skin is treated as urgent.

The NHS says most types of liver disease cause no symptoms in the early stages, and that once symptoms appear, such as tiredness, loss of appetite, itchy skin and jaundice, the liver is already damaged. See a GP if you think you might have liver disease.

The NHS pages above can be summarised into the following thresholds.

• Yellow skin or whites of the eyes, with or without itching, dark pee or pale poo: ask for an urgent GP appointment or get help from NHS 111. With severe tummy pain, a very high temperature or being sick, call 999 or go to A&E.

• Blood in the urine, or urine that is dark brown: the NHS says to ask for an urgent GP appointment or get help from NHS 111, even if there is only a small amount.

• Burning, frequency, back pain or fever with dark urine: the NHS says men and children, pregnant women, people over 65 and people with diabetes should ask for an urgent GP appointment or call NHS 111 for a suspected UTI.

• Dark urine that persists despite drinking enough, or that comes with unexplained tiredness, weight loss or loss of appetite: see a GP for a urine test and blood tests.

• Signs of serious dehydration such as dizziness on standing that does not go away, a fast heart rate, confusion or being difficult to wake need urgent care.

A GP will ask how long the urine has been dark, how much you drink, whether you have been unwell, which medicines and supplements you take, and about any pain, itching or change in stool colour. They may look for yellow eyes, feel the tummy and check hydration. The NHS says a urine sample and blood tests may be used when blood in the urine is suspected or an infection is possible.

Depending on the findings, blood tests may be used to look at liver function and to check for inflammation or anaemia, and ultrasound may be used to look for gallstones or bile duct problems. Treatment depends on the cause, from fluids and rest to antibiotics, gallbladder surgery, or specialist liver care.