Why do I have a bitter taste in my mouth?

Bitter is one of the five basic tastes, and our tongues are especially sensitive to it, probably because many toxins are bitter. A bitter taste with nothing in your mouth is a form of dysgeusia, a distorted taste. The NIDCD notes dysgeusia is sometimes accompanied by burning mouth syndrome, a painful burning sensation in the mouth, so mention any burning if you see a doctor.

1. Dehydration and dry mouth. Cleveland Clinic calls not drinking enough one of the leading causes, particularly in older adults, whose thirst signals weaken.
2. Acid reflux. Stomach contents rising into the throat leave a sour or bitter taste, worse after large meals and lying down.
3. Medicines and supplements. Many prescription and over-the-counter drugs, vitamins and supplements list a bitter taste or dry mouth as side effects, as does radiation to the head and neck.
4. Blocked nose. Colds, sinus infections, allergies and COVID-19 affect taste through smell and inflammation, and mouth breathing dries the tongue. Antihistamines and decongestants can add to it.
5. Oral health problems. Plaque, tooth decay, abscesses and infections. Oral thrush can cause an unpleasant taste and white patches; the NHS lists both.
6. Smoking. Damages taste buds, reduces saliva and raises the risk of gum disease.
7. Hormone changes. Pregnancy and menopause can both alter taste.
8. Aging. Taste and smell change with age, and older bodies hold less water.
9. Pine nuts. A delayed bitter or metallic taste lasting about 5 to 10 days, reported to the FDA after eating certain pine nuts.
10. Other conditions. Cleveland Clinic notes diabetes, thyroid disease, nerve damage, head injury and liver or kidney disease can affect taste, usually with other symptoms.

A bitter taste on waking usually points to one of three things: reflux while lying flat at night, mouth breathing from a blocked nose, or simple overnight dryness while saliva flow is low. Reflux tends to come with heartburn or a sore throat in the morning; mouth breathing comes with a dry tongue and snoring. If the taste vanishes after breakfast and a glass of water, dryness is the likeliest explanation.

• Drink more water. Cleveland Clinic calls hydration the single most important step. Unsweetened herbal tea or sparkling water count too.
• Chew sugar-free gum to boost saliva, which washes away food particles and acid.
• Rinse with baking soda: half a teaspoon in warm water, swish and spit.
• Deal with reflux at night: avoid eating right before bed and raise the head of the bed by 4 to 6 inches or use a wedge pillow.
• Clean your teeth and tongue twice a day and floss once.
• Review medicines with your doctor or pharmacist rather than stopping them yourself.

Cleveland Clinic advises seeing a provider if a bitter taste lasts more than a week, gets worse, or comes with symptoms beyond the mouth such as unexplained weight loss or fatigue. Frequent reflux may be GERD and need prescription treatment. A dentist is the right first stop if you also have toothache, swollen gums or white patches.