What should I watch for?
Visit your doctor or health care professional for regular checks on your progress. You will need blood work done regularly.
You may need to take vitamin supplements while on this medicine. Talk to your doctor about the foods you eat and the vitamins you take. Avoid taking antacids containing aluminum, calcium or magnesium, and iron-containing products within 2 hours of taking this medicine. It is best to separate these medicines by 4 to 6 hours.
If you are diabetic, monitor your blood sugars closely. This medicine may change the way your diabetic medicine works, and sometimes will require that your dosages be adjusted. Check with your doctor or health care professional.
If you have diabetes, you may get a false-positive result for sugar in your urine. Check with your doctor or health care professional.
This medicine can cause serious liver problems. Make sure you understand the risks for liver problems and how to identify the symptoms. If you have any questions, talk with your doctor or other health care provider.
Avoid alcoholic drinks while you are taking this medicine. Drinking alcohol during treatment with this medicine increases the risk of serious liver problems.
This medicine can color your urine, feces (stool), perspiration (sweat), tears, sputum, skin or saliva reddish-orange to reddish-brown. This color can last for as long as you take this medicine and is not a cause for alarm. This color in tears may permanently stain soft contact lenses. It is better not to wear soft contact lenses while you are taking this medicine.
This medicine can make you more sensitive to the sun. Keep out of the sun. If you cannot avoid being in the sun, wear protective clothing and use sunscreen. Do not use sun lamps or tanning beds/booths.
You may get a false-positive result for sugar in your urine while you are taking this medicine. Talk with your doctor.
Common and Rare Side Effects
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:
Clumsiness or unsteadiness
loss of appetite
numbness, tingling, burning, or pain in the hands and feet
pain in large and small joints
unusual tiredness or weakness
yellow eyes or skin
difficulty with breathing
muscle and bone pain
redness of the skin
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:
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.