Blood in mucus (from the nose, throat, or when you cough) can be from something mild like irritation from a bad cough or dry air, but it can also signal a more serious problem in the lungs or airways. Because the range is wide, any new, repeated, or heavy bleeding should be checked by a doctor or urgent care, especially if you feel unwell.

Common less-serious causes

These are frequent reasons for small streaks or spots of blood in mucus:

• Hard or frequent coughing that irritates and breaks tiny blood vessels in your airways.
• A recent or current cold, flu, bronchitis, or other chest infection.
• Nosebleeds or very dry nasal passages; blood from the nose can drain backward and appear in mucus you spit out.
• Throat irritation from smoking, vaping, allergies, or acid reflux.

With these, the amount of blood is usually small, streaky, and tends to improve over a few days as the cough or irritation gets better.

Concerning causes that need urgent care

Blood in mucus can also come from more serious conditions, especially if there is more than a trace or it keeps happening:

• Pneumonia or more severe lung infections.
• Blood clots in the lungs (pulmonary embolism).
• Tuberculosis or other serious infections.
• Chronic lung diseases (like bronchiectasis, severe COPD).
• Lung or throat cancer.
• Side effects of blood thinners or a bleeding/clotting problem.

Go to emergency care or call emergency services right away if:

• You cough up more than a small streak (for example, a teaspoon or more, or repeated clots).
• You are short of breath, have chest pain, feel faint, or have a fast heartbeat.
• You have high fever, night sweats, or unexplained weight loss.
• You recently had major surgery, long travel/immobility, or leg swelling (possible blood clot).

What you should do now

Because this can sometimes be serious, it is safest to:

• Contact a doctor, urgent care, or nurse line today, especially if:
  • This is new and unexplained.
  • The blood has happened more than once.
  • You also have cough, fever, chest pain, or feel short of breath.
• If you are on blood thinners (like warfarin, apixaban, rivaroxaban, heparin, etc.), treat any new bleeding as urgent and call your prescriber or seek care.
• Try to note:
  • How much blood (tiny streaks vs. clots or more).
  • Color (bright red vs. dark/brown).
  • Whether it is from the nose, throat, or clearly from a deep cough.
  • Any other symptoms (fever, weight loss, night sweats, chest pain, shortness of breath, recent infections, travel, or injuries).

If you tell more details—your age, whether it’s coming from your nose vs when you cough, how much blood, and any other symptoms—a more tailored explanation and urgency estimate can be given. But this does not replace seeing a doctor in person, which is very important when blood is involved.