In order to explain what causes bedwetting, it helps to understand how the bladder works. Look at our daytime wetting section to find out more about the bladder.

There are three main reasons why children wet the bed:

  1. Their bladders don’t stretch enough to hold all the wee they make at night.
  2. They produce too much wee at night.
  3. They don’t wake up when their bladder sends a signal that it’s full.

Night time accidents can be caused by one or more of these reasons. The good news is, all are treatable.

Bedwetting also runs in families. If one parent wet the bed, their child has a 40% chance of doing the same; if both parents wet the bed, there’s a 70% chance. 

1. The bladder doesn’t stretch enough 

Constipation could be the cause

If your child is constipated, their bowel is full of poo. A full bowel can press against the bladder, limiting the space it has to stretch and fill. As a result, your child feels the urge to wee frequently and has to do lots of little wees. This can cause wetting accidents during the day or night.

For more information on children’s bowel problems and how to treat constipation, look at the bowel problems section and download ERIC’s Guide to Children’s Bowel Problems.

Treatment: An assessment by a doctor and laxative medication is usually needed to sort out childhood constipation.

An overactive bladder could be the cause

The bladder may be 'overactive' and give an urgent signal to empty before it’s full. An overactive bladder usually holds lower than average amounts of wee. Signs of an overactive bladder are:

  • Urgency to wee and weeing more frequently than normal (more than eight times a day).
  • Smaller patches of wee in the bed, indicating that the bladder is emptying more frequently and in small amounts.
  • Wetting often occurs more than once a night and the child may wake afterwards.

Treatment: Exercising the bladder can help tackle wetting accidents that are the result of an overactive bladder. Exercises involve filling and emptying the bladder properly throughout the day (see the daytime wetting page for more information on bladder exercise).

Medication such as Oxybutynin or Tolterodine is sometimes prescribed for an overactive bladder to relax the muscles.

2. Your child produces too much wee at night

Low levels of vasopressin could be the cause

The hormone vasopressin tells the kidneys to make less wee at night. If a child doesn’t produce enough vasopressin while they’re asleep, they make more wee than their bladder can hold.

There’s no test to check vasopressin levels, but signs that your child might not have enough of the hormone include:

  • Regular wetting, sometimes more than once a night.
  • The first accident could be within a couple of hours of going to sleep.
  • Your child is unlikely to wake up and their nappy, if they wear one, will be very heavy and may leak. If they don’t wear a nappy, the patches of wee will be large and light yellow, without too strong a smell.

Treatment: An artificial form of vasopressin, called Desmopressin, can be prescribed by a doctor to ‘top up’ your child’s natural levels of the hormone. Desmopressin can be taken just before bedtime either for one-off nights away or it can be taken longer term until your child’s own levels of vasopressin are high enough to regulate the wee produced at night.

Take a look at ERIC’s Guide to Night Time Wetting and factsheet Using Desmopressin as a Treatment for Bedwetting for more information on using Desmopressin.

3. Your child doesn’t wake up to full bladder signals

Some children just don’t wake up when their bladder tries to tell them it’s full or they wake just afterwards when it’s too late.

Treatment: A bedwetting alarm can be a successful way of training the brain to respond to the bladder’s signals. The alarm goes off as soon as the child starts to wee; over time your child will learn to wake up and go to the loo when their bladder is full.

For more information on alarms take a look at ERIC’s Guide to Night Time Wetting and supplement Bedwetting Alarms - Your Questions Answered.

We sell a wide range of alarms in the ERIC shop including body-worn alarms and bed mat devices. We can explain what types of alarms are available and how best to use them.

Other causes of bedwetting 

Urinary Tract Infection (UTI)

Symptoms of a UTI will be noticeable during the day and may affect a child’s ability to stay dry at night as well. Signs of a UTI include:

  • Wee that is fishy smelling, cloudy or bloodstained
  • High temperature
  • Vomiting
  • Difficulty or discomfort when weeing
  • Often wet or damp during the day as well as at night.

Treatment: See your GP for a urine test to check if your child has a UTI. If the test is positive, the doctor will prescribe antibiotics to clear up the infection.

Anxiety and stress

Bedwetting can be triggered in children who were once dry at night by anxieties or stresses such as an illness, starting school, moving house, a new baby, exams or any other big life changes. Wetting again after a period of dryness is known as late-onset or secondary nocturnal enuresis.

Treatment: Secondary nocturnal enuresis is treated in the same way as bedwetting.

Other illnesses

Bedwetting can also be a symptom of other illnesses such as diabetes. Children should therefore always be checked by a doctor to find out if there is another cause.

Now read our information on how to stop or manage bedwetting.