- Waking up at night to urinate (nocturia) can impact the quality of sleep.
- In people with no medical conditions, caffeine, fizzy drinks and excessive fluid intake at night can be a major cause of nocturia.
- This is partly due to suppression of a key hormone called antidiuretic hormone (ADH).
- Hydration is important but many people drink too much fluid in the evening rather than spreading it out during the day.
- Other causes include overactive bladder, altered circadian rhythm and medical conditions such as sleep apnoea and diabetes.
Do you often wake up at night needing to urinate? Waking up even once can have a significant impact on our sleep quality especially if you stay awake for more than a few minutes. For some people who have trouble falling back asleep this can be a big problem. Waking up frequently can also impact the amount of important sleep stages such as deep and REM sleep we would otherwise be getting.
The condition of waking up to urinate one or more times a night is called nocturia. It can have many causes, some serious and others less so. In this article I will focus on the most common causes of nocturia in people with no medical conditions, namely drinking too much fluid at night and bladder overactivity often caused by bladder irritants such as caffeine. . It is important to take into consideration other causes of nocturia. These can include medical conditions such as prostate enlargement, urinary infections, overactive bladder and side effects of certain medications.
How does drinking too much fluid cause nocturia?
One of the main hormones involved in urination is the antidiuretic hormone (ADH, also called vasopressin). As the name suggests, one of the effects of ADH is to suppress urination and conserve the body’s fluid. ADH responds to changes in the concentration of fluid (more specifically, the tonicity) as a measure of the amount of fluid in our bodies. It is elevated when the fluid concentration is lower than normal in an effort to conserve fluid and is suppressed when there is excess fluid (lower tonicity).
Normally, ADH levels increase during sleep. This keeps us from forming more urine and needing to get up to urinate at night. If for some reason the secretion of ADH is suppressed, this can lead to the formation of more and therefore nocturia. Causes of ADH suppression can be caused by certain behaviours or medical conditions.
Behavioural causes of ADH suppression include:
- Increased fluid intake: Excessive fluid intake directly suppresses ADH secretion. As explained earlier, ADH regulates fluid levels in our body and promotes getting rid of excess fluid. If we consume more fluid than we actually need, our bodies will want to get rid of that fluid in the form of urine leading to nocturia.
- Caffeine intake: caffeine has been shown to have an effect on ADH secretion and is considered a diuretic. The half-life of caffeine can be close to 5 hours which means that the effects of caffeine can last for a very long time after consuming it. This is another reason why limiting caffeine intake to the early parts of the day is a wise idea.
- Alcohol: drinking alcohol at night is an independent cause of ADH suppression. This can lead to dehydration and can explain why excessive drinking can cause a “hangover” in the morning. Hangovers are mostly caused by dehydration.
Think about what and when you drink
Many people feel the need to reach certain daily targets when it comes to fluid intake. Others get swept up on their jobs or meetings where grabbing a drink isn’t always practical. Regardless for many, most fluid intake is in the evening with their meal. Remember that the meal itself may have a high water content. If it is too close to bedtime, this can lead to nocturia, as fluid takes between 3 and 4 hours to pass through our systems thus resulting in night-time waking to pass urine.
I’m not against trying to meet hydration targets, they are a great prompt to remind us to adequately hydrate. We know that mild dehydration can affect muscle function and power as well as cognition. Very concentrated urine can in-fact irritate the bladder. Try to drink water throughout the day rather than storing it up to drink in the evening. Try to stop drinking 3 to 5 hours before you go to bed. This may mean you need to eat dinner a little earlier.
Overactive bladder (OAB) is another well recognised cause of nocturia. OAB also causes daytime frequency of urine (>8 voids/day) and the inability to delay voiding. Those affected normally pass only small volumes (<200mls of urine). If this is something that affects you then it is likely to be contributing to the nocturia. If you’re not sure, you could complete a bladder diary to find out (see link below). OAB can be caused by caffeine, fizzy drinks or spicy food. This can be a particular problem at night. Most urologists recommend switching to decaffeinated coffee and tea or cutting them out completely. You could also try bladder retraining (see link) as bladder capacity and behaviour is a learned behaviour that can be modified.
It’s important to recognise that circadian rhythm also affects ADH production. If you’re someone that travels frequently, or does trans atlantic/pacific meetings at night, this will affect your circadian rhythm and likely cause nocturia. Exercise too late in the day can alter circadian rhythm and you could consider optimising your exercise schedule to be in the earlier parts of the day. I wrote more about how to reset your circadian rhythm here. Similarly conditions that cause frequent waking such as anxiety, depression and sleep apnoea can also contribute. Treatment of these conditions will help manage the nocturia.
If you are someone who oftens wakes at night, and passes urine because you’re already up, stop! Ask yourself if you really need to urinate. This is negative reinforcement of the altered circadian rhythm.
Take home message
If you find yourself waking up at night once or more to urinate, you may want to consider limiting fluid intake 3-5 hours before going to bed. Think about spreading out your fluid intake across the day and remember that caffeine, alcohol and fizzy drinks are well recognised bladder irritants. It is always best to consult with a medical professional to exclude other causes if you have these symptoms especially alongside painful urination or blood in the urine.
Input output chart.pdf (baus.org.uk)
Bladder training.pdf (baus.org.uk)