Why does my mouth taste bitter when I wake up?

Waking up with a bitter taste in your mouth could have several different causes:

• Poor oral hygiene means food particles remain in your mouth instead of being brushed and flossed away. Bacteria acting on the particles can cause a bad taste in your mouth.
• Dry mouth (xerostomia) can cause a bitter taste in the mouth. You might have dry mouth in the morning from breathing through your mouth while you sleep.
• Some medications can cause dry mouth or a bitter or metallic taste in the mouth.
• Smoking and using tobacco products can cause bad breath, and result in a bitter taste in your mouth upon waking.
• Health problems -- such as a sinus infection, postnasal drip, or diabetes -- can cause a bad taste in the mouth both during the day and upon waking.
• Certain foods can cause bad breath or a bad taste in the mouth.

Talk to your doctor or dentist if you think the bitter taste in your mouth in the morning is caused by dry mouth, a health problem, or a drug you take.

When you sleep, you have a decreased flow of saliva. Breathing through the mouth continuously can also cause dry mouth and bad breath. Both can happen while you're sleeping, resulting in bad breath in the morning. 

If you wear dentures, be sure to remove them at night and clean them thoroughly before replacing them the next morning.

Brush twice a day and clean between your teeth daily with floss. Brush your tongue, too. 

If bad breath is more frequent, talk to your dentist. He or she can help to diagnose the cause.