Why do I wake up with a dry mouth?

You usually wake up with a dry mouth because you spent part of the night breathing through your mouth, either because your nose was blocked or because your mouth fell open as you slept. Medicines, not drinking enough and alcohol can add to it. Less often, a dry mouth on waking is one sign of obstructive sleep apnea, especially alongside loud snoring and daytime sleepiness.

Why does mouth breathing dry you out?

Mouth breathing dries you out because it skips the nose, where air picks up moisture on the way in. Breathing through your mouth skips that step, and air moving over your tongue and gums for hours evaporates the saliva that normally keeps them wet. Your body also makes less saliva while you sleep, so it can't keep up.

The NHS lists breathing through your mouth at night as one of the main causes of a dry mouth, and says it can happen if you have a blocked nose or simply sleep with your mouth open. Cleveland Clinic makes the same point from the other direction: breathing through your nose helps keep moisture in your mouth and throat.

Plenty of people fall asleep breathing through their nose and only switch later, once the jaw relaxes and the lips part. That's why you can feel fine going to bed and still wake up dry.

Why does a dry mouth matter?

A dry mouth matters because saliva does more than keep your mouth comfortable. The National Institute of Dental and Craniofacial Research (NIDCR) explains that it washes food particles off the teeth and gums and contains minerals like calcium and phosphate that help keep teeth strong. When dry mouth persists, it raises the risk of tooth decay and fungal infections in the mouth, because saliva helps keep harmful germs in check.

The NHS gives the same warning, noting that you're more likely to get tooth decay with a dry mouth. So a parched mouth most mornings is worth fixing for your teeth as well as for comfort. Our guides to mouth breathing and your teeth and mouth breathing and bad breath go into this further.

When can it point to sleep apnea?

Mayo Clinic lists waking up with a dry mouth as one of the symptoms of obstructive sleep apnea. A prospective case-control study from Spain compared 60 adults recently diagnosed with sleep apnea with 54 healthy people. Dry mouth on waking affected 45% of the sleep apnea group and 20.4% of the healthy group. During the rest of the day the numbers fell in both groups, to 21.7% and 9.3%. Dry mouth was also more common in moderate sleep apnea than in mild cases.

For context, the same paper notes that dry mouth is very common in the general population, with estimates ranging from 5% to 46%. So dry mouth on its own doesn't mean you have sleep apnea. But take it seriously if it comes with any of these, which the American Academy of Sleep Medicine lists as warning signs: loud snoring, choking or gasping in your sleep, pauses in your breathing that someone else has noticed, or feeling tired during the day after a full night in bed.

If you want to try mouth tape, our pick is the Titan Bamboo Silk Mouth Tape.

Can CPAP cause a dry mouth?

Yes, CPAP can cause a dry mouth. In the same Spanish study, dry mouth on waking was reported by 57.1% of people with sleep apnea who were using CPAP, compared with 16.7% of those who weren't. SleepApnea.org says dry mouth on CPAP is often caused by breathing through the mouth or by mask leaks, and that many people improve it with a heated humidifier, a better mask fit, treating nasal congestion or switching to a full-face mask.

If you use CPAP, talk to your sleep doctor or CPAP provider before you change anything. Our article on mouth tape and CPAP covers the options they may suggest.

What else can cause it?

• Medications. The NIDCR says hundreds of medicines can make the salivary glands produce less saliva, including some for high blood pressure, depression and bladder control.
• Not drinking enough. The NHS lists dehydration from not drinking enough, sweating a lot or being ill.
• A blocked nose from a cold, allergies or a deviated septum, which pushes you to breathe through your mouth.
• Dry air in the bedroom, especially with the heating on.
• Alcohol and tobacco, which the NIDCR says dry out the mouth.
• Conditions such as diabetes and Sjögren's syndrome, which the NHS says can sometimes cause a dry mouth that doesn't go away.

If you think a prescribed medicine is the cause, the NHS advises not stopping it without medical advice. Ask your doctor or pharmacist instead.

What can you try tonight?

Tonight, start by working out whether your nose is the problem. If it feels blocked when you lie down, a nasal strip can make it easier to breathe through, and a doctor can check for anything structural. Cleveland Clinic otolaryngologist Dr. Michael Benninger recommends nasal strips or a steroid nasal spray for longer-term relief of congestion. If you use a decongestant spray, read about decongestant spray rebound first.

If your nose is clear and your mouth just falls open, mouth tape is the simplest way many adults keep their lips closed overnight. The Sleep Foundation says supporters of mouth taping describe benefits such as less dry mouth, though this hasn't been well studied yet. If you try it, use a porous tape made for skin, check you can breathe comfortably through your nose with the nose test, and read is mouth taping safe? before your first night. If your lips get dry too, see lip balm and mouth tape.

The NHS also suggests a few simple things that ease a dry mouth whatever the cause:

• Keep some water by your bed at night and take regular sips during the day.
• Chew sugar-free gum or suck sugar-free sweets.
• Use lip balm if your lips are dry.
• Brush twice a day and use an alcohol-free mouthwash.
• Don't drink lots of alcohol, caffeine or fizzy drinks.

If the air in your bedroom is dry, a humidifier is another option to consider.

When should you see a doctor?

The NHS suggests seeing a GP if your mouth is still dry after trying home or pharmacy treatments for a few weeks, if it makes talking or eating difficult, if your mouth is painful, red, swollen or bleeding, if you have sore white patches, or if you have other symptoms like needing to pee a lot or dry eyes. The NIDCR adds that a doctor or dentist may review your medicines and suggest tests, including one that measures how much saliva you make.

If your dry mouth comes with loud snoring, gasping or heavy daytime sleepiness, see a doctor about sleep apnea first. Our guide to snoring vs. sleep apnea explains the difference.

Read next

• Why do I breathe through my mouth at night?
• Nasal breathing vs. mouth breathing
• Why do I wake up with a sore throat?

* This content is for informational and educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure or prevent any disease or health condition. Talk to a qualified healthcare provider about your health.