Comfort and side effects
CPAP Dry Mouth: Causes and Fixes
Dry mouth on CPAP usually means air is escaping through your mouth, your humidity is too low, or your mask is leaking. Turning up humidification, keeping your mouth closed with a chinstrap, or switching to a full face mask fixes it for most people.
Signs
- Waking with a parched mouth, tongue or lips
- Sore or scratchy throat in the morning
- Needing water several times a night
- Cracked lips
- Your humidifier tub is empty by morning
Common causes
- Mouth breathing with a nasal or pillows mask
- If your mouth falls open while you sleep, pressurized air flows in through your nose and straight out of your mouth. That stream of air dries your mouth fast and also lowers the pressure that reaches your airway.
- Humidity set too low
- CPAP air is drier than the air your nose normally warms and moistens. The AirSense 11 user guide lists a dry or blocked nose and mouth dryness as signs the humidity level may be set too low.
- Mask leak
- ResMed notes that severe mask leak can cause dry mouth whether or not your machine has a humidifier, and it also makes therapy less effective.
- Heated air losing its moisture
- If the tube or humidifier runs too hot, the air can lose moisture before it reaches you. ResMed warns that settings set too high can bring the dryness back.
- Medicines and dehydration
- Some medicines list dry mouth as a side effect, and not drinking enough during the day makes it worse. F&P suggests drinking water through the day to lower the chance of dehydration.
Fixes to try, easiest first
Drink water during the day
Start with the easy part. Fisher & Paykel suggests drinking water throughout the day so you are not going to bed already dehydrated.
Keep a glass of water by the bed for the first few weeks, but if you are waking up thirsty every night, treat that as a sign that one of the fixes below is needed.
Check your mask fit while lying down
Put your mask on, lie down in your usual sleep position and turn the air on. Pull the mask slightly away from your face and let it reseat, then adjust the straps until it seals without being tight.
If your machine has a Mask Fit feature (ResMed AirSense 11 has one in the menu), run it to check the seal. Do not crank the straps tighter to stop a leak, because overtightening causes marks and can make leaks worse.
Turn up the humidity one step at a time
Humidity is a comfort setting you can usually change from the patient menu. ResMed suggests changing humidity and tube temperature one notch at a time so you can tell what helped.
If you reach the top setting and still wake up dry, stop raising it and look for mask leak or mouth leak instead. An empty water tub in the morning is another clue that leak is the real problem.
Use heated tubing or Climate Control
Heated tubing keeps the air warm and moist all the way to your mask. On ResMed machines with a ClimateLineAir tube, Climate Control Auto aims for a steady humidity level and adjusts for your room.
If you are on a standard tube in a cold bedroom, ask your equipment provider whether heated tubing works with your machine.
Try a chinstrap
If you wear a nasal or pillows mask and wake up with your mouth open, a soft chinstrap can help hold your jaw closed. F&P and the AirSense 11 user guide both suggest a chinstrap for air escaping through the mouth.
Some people find chinstraps too tight or dislike another strap. If it is uncomfortable after a week or two, move on to a full face mask.
Ask about a full face mask with your clinician
A full face mask covers your nose and mouth, so air that leaves through your mouth stays in the system. ResMed says a full face mask is usually the best solution for mouth leak.
Ask your equipment provider for a fitting. Bring your current mask so they can see what is happening.
Review your medicines with your doctor with your clinician
If you take medicines that cause dry mouth, ask your doctor or pharmacist whether any could be changed. Do not stop a prescribed medicine on your own.
Call your sleep doctor or equipment provider if dry mouth keeps you from using CPAP all night, if you have reached the highest comfortable humidity setting and are still dry, or if your machine data shows high leak. Your clinician can review your data, check your mask type and look at medicines that cause dryness. See your dentist if you notice tooth or gum problems, since a dry mouth for long periods can affect your teeth.
Supplies that can help
A soft strap that supports the jaw to help keep the mouth closed, used mainly with nasal and nasal pillow masks to reduce mouth leaks.
Tubing with a built-in heating wire that keeps humidified air warm all the way to the mask, which is the main fix for rainout (water droplets …
Distilled water is what most CPAP humidifier chambers are meant to be filled with, because it leaves little or no mineral scale behind.
The removable water tank of a CPAP humidifier; it wears and needs replacing, especially if it cracks, clouds or leaks.
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Mask types this applies to
Frequently asked questions
Why do I wake up with a dry mouth on CPAP even with the humidifier on?
The most common reason is that air is leaving through your mouth, which a humidifier cannot keep up with. Check for mouth leak with a nasal or pillows mask, and check whether your water tub is empty by morning. A chinstrap or full face mask usually solves it.
Is mouth tape safe to use with CPAP?
Some people use mouth tape to keep their lips closed with a nasal mask, but ask your sleep doctor first. It is not a good choice if your nose is often blocked, because you need a way to breathe if your nose is congested or the machine stops.
Can a full face mask cause dry mouth too?
Yes. If the full face mask leaks or the humidity is low, you can still wake up dry. Check the seal while lying in your sleep position and raise the humidity one step at a time.
Does dry mouth mean my CPAP is not working?
Not always, but mouth leak can lower the pressure that reaches your airway. If you also see a high leak number or a rising AHI in your app, tell your provider.
Sources
Last reviewed October 11, 2026. How we research · Report an error