You should not take ribavirin if you are allergic to it, or if you have:

severe liver disease (especially cirrhosis);
autoimmune hepatitis;
a hemoglobin disorder such as anemia, thalassemia (Mediterranean anemia), or sickle-cell anemia;
if you are also taking didanosine (Videx); or
if you are pregnant woman, or a man whose female sexual partner is pregnant.

To make sure you can safely take ribavirin, tell your doctor if you have any of these other conditions:

kidney or liver disease (other than hepatitis C);
hepatitis B infection;
a blood cell disorder such as hemolytic anemia (a lack of red blood cells);
human immunodeficiency virus (HIV or AIDS);
diabetes;
a pancreas disorder;
sarcoidosis;
breathing problems;
a thyroid disorder;
new or worsening eye problems (such as retinopathy);
a history of heart disease, high blood pressure, or a heart attack;
a history of depression or suicide attempt;
a history of a liver, kidney, or other organ transplant; or
if you have ever received treatment for hepatitis C that did not work well.

This medication can cause birth defects or death in an unborn baby.

If you are a woman, do not take ribavirin if you are pregnant. You will need frequent pregnancy tests to make sure you are not pregnant while taking ribavirin.

If you are a man, do not take ribavirin if your female sexual partner is pregnant. An unborn baby could also be harmed if a man fathers the child while he is taking ribavirin. 

Use at least two effective forms of birth control while either sexual partner is taking ribavirin, and for at least 6 months after treatment ends.

Tell your doctor right away if a pregnancy occurs while either the mother or the father is taking ribavirin.

It is not known whether ribavirin passes into breast milk or if it could harm a nursing baby. You should not breast-feed while you are taking ribavirin.

Ribavirin may affect growth in children.

Stop using ribavirin and call your doctor at once if you have a serious side effect such as:

problems with your vision;
fever, chills, body aches, flu symptoms;
severe pain in your upper stomach spreading to your back, nausea and vomiting, fast heart rate;
stabbing chest pain, wheezing, feeling short of breath;
severe depression, hallucinations, thoughts of suicide or hurting yourself;
chest pain or heavy feeling, pain spreading to the arm or shoulder, nausea, sweating, general ill feeling; or
pale or yellowed skin, dark colored urine, easy bruising or bleeding, confusion, or unusual weakness.

Less serious side effects may include:

headache;
muscle pain;
dry mouth;
nausea; vomiting, stomach pain, loss of appetite;
weight loss;
feeling tired or irritable;
anxiety, mood changes; or
pain, swelling, or irritation where the interferon injection was given.