Side Effects

Drug information provided by: Micromedex

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

More common

  1. Clumsiness or unsteadiness
  2. dark urine
  3. loss of appetite
  4. nausea and vomiting
  5. numbness, tingling, burning, or pain in the hands and feet
  6. pain in large and small joints
  7. unusual tiredness or weakness
  8. yellow eyes or skin

Less common

  1. Chills
  2. difficulty with breathing
  3. dizziness
  4. fever
  5. headache
  6. itching
  7. muscle and bone pain
  8. redness of the skin
  9. shivering
  10. skin rash


  1. Bloody or cloudy urine
  2. blurred vision or loss of vision, with or without eye pain
  3. convulsions (seizures)
  4. greatly decreased frequency of urination or amount of urine
  5. mental depression
  6. mood or mental changes
  7. sore throat
  8. unusual bleeding or bruising

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

  1. Diarrhea
  2. stomach pain

Less common

  1. Sore mouth or tongue

This medicine commonly causes urine, stool, saliva, sputum, sweat, and tears to turn reddish-orange to reddish-brown. This side effect does not usually require medical attention.

Dark urine and yellowing of the eyes or skin (signs of liver problems) caused by isoniazid are more likely to occur in patients 50 years of age and older.

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.