Depending on how much of your body weight is lost through fluids, dehydration can be described as mild, moderate or severe.
Mild to moderate dehydration
The first sign of dehydration is thirst. Other symptoms may include:
- dizziness or light-headedness
- headache
- tiredness
- dry mouth, lips and eyes
- concentrated urine (dark yellow)
- passing only small amounts of urine infrequently (less than three or four times a day)
Moderate dehydration causes you to lose strength and stamina. It's the primary cause of heat exhaustion. You should be able to reverse mild to moderate dehydration by drinking more fluids, without medical attention.
If dehydration is ongoing (chronic), it can affect your kidney function and cause kidney stones to develop. It can also cause:
- liver, joint and muscle damage
- cholesterol problems
- constipation
Severe dehydration
Untreated mild or moderate dehydration can lead to severe dehydration.
Severe dehydration is a medical emergency and requires immediate medical attention. You should seek medical attention if you or your child has any of the following symptoms:
- dry, wrinkled skin that sags slowly into position when pinched up
- an inability to urinate, or not passing urine for eight hours
- irritability
- sunken eyes
- low blood pressure (hypotension)
- a weak pulse
- a rapid heartbeat
- cool hands and feet
- fits (seizures)
- a low level of consciousness
- feeling tired (lethargic) or confused
- blood in your stools (faeces) or vomit
If not treated immediately, severe dehydration can lead to complications. You can even die from severe dehydration because the blood stops circulating. If you experience this level of dehydration, you may need to be admitted to hospital and be put on a drip to restore the substantial loss of fluids.
When should I see my GP?
You should visit your GP if your symptoms continue, despite drinking plenty of fluids or if you suspect that your baby or toddler is dehydrated.
If your doctor suspects dehydration, you may be given a blood test or a urine test to check the balance of salts (sodium and potassium) in your body.
Contact your GP or out-of-hours service straight away if you have any of the following symptoms:
- feeling tired (lethargic) or confused
- dry mouth and eyes that don't produce tears
- not passing urine for eight hours
- dry skin that sags slowly into position when pinched up
- rapid heartbeat
- blood in your stools (faeces) or vomit
- low blood pressure (hypotension)
Also contact your GP if you or your child has diarrhoea that lasts longer than five days, or vomiting that lasts more than 24 hours in adults or 12 hours in a child.
