Why do I taste blood in my mouth?

Spit into a white tissue or the sink. Pink or red streaks mean there is blood, and the job is to find where it comes from. If you see nothing, you are more likely dealing with a metallic taste caused by a medicine, supplement, infection or pregnancy, which our metallic taste page covers.

Check your gums along the tooth line, the inside of your cheeks, your tongue and the back of your throat in good light. Note whether the taste is worse after brushing, in the morning, or after blowing your nose.

• Gum disease. The NHS describes bleeding when you brush, floss or bite into hard food such as an apple as the main symptom. It is very common and can also cause bad breath and a bad taste.
• Brushing too hard or starting to floss. Gums often bleed for the first days of a new flossing habit and settle within a week or two if the gums are healthy.
• Dental work, a lost tooth or an extraction site. Some oozing is expected for a short time afterwards.
• Mouth injuries and ulcers. Biting your cheek or tongue, sharp food or a broken tooth edge.
• Nosebleeds and nasal crusting. Blood can run down the back of the throat, especially at night. Colds, sinusitis and dry air make the lining of the nose more fragile.
• Blood-thinning medicines. People on anticoagulants bleed more easily from the gums and nose.

Some people notice a blood or metallic taste during very hard exercise. The reason has not been well studied; if it happens with chest pain, breathlessness out of proportion to the effort or coughing up blood, stop and get checked.

Gums: keep brushing twice a day with a soft brush angled at the gum line and clean between your teeth daily. Stopping because of bleeding lets plaque build up and makes bleeding worse. The NHS advises seeing a dentist if your gums bleed when you brush or eat, or are painful and swollen, because tartar below the gum line needs professional cleaning.

Nosebleeds: the NHS advises sitting down, leaning forward with your mouth open, and pinching the soft part of the nose just above the nostrils for 10 to 15 minutes while breathing through your mouth. Leaning forward stops blood running down your throat, which is what causes the taste and can make you feel sick.

The NHS lists a long-lasting or severe cough, chest infections, pneumonia, tuberculosis, bronchitis and bronchiectasis as common causes of coughing up blood, and blood clots in the lung or lung cancer as less common but serious ones. Vomiting blood is often a sign of bleeding in the stomach or esophagus, for example from an ulcer, although swallowed blood from a nosebleed can also be vomited. Both need medical assessment, and the thresholds are in the warning signs on this page.