Causes of bedwetting 

Bedwetting is not your child's fault and there's often no obvious reason why it happens. In many cases, the problem runs in families.

Most experts believe there may be more than one underlying cause.

Bladder problems

The bladder is a balloon-like organ in the pelvis that stores urine. When it's full, urine flows out of it through a tube called the urethra, found in the centre of the penis in boys and just above the main opening of the vagina in girls.

Some children affected by bedwetting have 'overactive bladder syndrome'. This is where the muscles that control the bladder go into spasm, leading to the involuntary leaking of urine.

Producing lots of urine

Drinking lots of fluids during the evening could cause your child to wet the bed during the night, particularly if they have a small bladder capacity. Drinks containing caffeine, such as cola, tea, and coffee, can also stimulate an increase in the production of urine.

In some cases of bedwetting, the child’s body doesn't produce enough of a hormone called vasopressin, which regulates urine production. This means their kidneys produce too much urine for their bladder to cope with.

Not using the loo during the night

Once the amount of urine in the bladder reaches a certain point, most people wake up as they feel the need to go to the toilet. However, some younger children are particularly deep sleepers, and their brain doesn't respond to signals sent to the brain from their bladder, so they don't wake up.

Alternatively, in some children the nerves attached to the bladder may not yet be fully developed, so they don't generate a strong enough signal to send to the brain.

Sometimes, a child may wake up during the night with a full bladder but not go to the toilet. This may be because of childhood fears, such as being scared of the dark.

Underlying health condition

Bedwetting can also be caused by an underlying health condition, such as:

  • constipation – if a child’s bowels become blocked with hard stools, it can put pressure on the bladder and lead to bedwetting
  • type 1 diabetes – a lifelong condition that causes a person's blood sugar level to become too high and can result in producing lots of urine
  • a urinary tract infection (UTI)
  • abnormalities with the urinary tract, such as bladder stones 
  • damage to the nerves that control the bladder – this could be caused by an accident or a condition such as spina bifida

Emotional problems

In some cases, bedwetting can be a sign that your child is upset or worried. Starting a new school, being bullied, or the arrival of a new baby in the family can be very stressful for a young child.

If your child has started wetting the bed after previously being dry for a period of six months or more (known as secondary nocturnal enuresis), emotional problems such as stress and anxiety may be responsible.

Page last reviewed: 27/03/2015

Next review due: 27/03/2017