Anti-thyroid medications can cause liver damage and reduced blood cell production in some patients.

We analyzed the available evidence and found that 35 studies and assertions support the idea that anti-thyroid medications can lead to liver damage and reduced blood cell production in some people [1]. No studies or assertions in our review contradicted this. What we’ve found so far suggests that these side effects, while not common in everyone, are documented enough to be considered a potential risk. Liver damage may show up as elevated liver enzymes, jaundice, or abdominal pain, while reduced blood cell production can mean lower levels of white blood cells, red blood cells, or platelets — which can increase infection risk or cause fatigue and bruising. These reactions are rare overall, but when they happen, they can be serious. The evidence we’ve reviewed does not tell us how often this occurs in the general population, nor does it identify exactly who is most at risk. We also don’t have enough detail to say whether certain medications, doses, or patient traits make these effects more likely. Because these side effects are rare but potentially severe, the current evidence leans toward the importance of monitoring — especially in the first few months of treatment. Regular blood tests and liver function checks are often recommended, not because these problems happen often, but because catching them early can prevent worse outcomes. If you’re taking anti-thyroid medication, talk to your doctor about signs to watch for — like unexplained fatigue, yellowing skin, dark urine, or frequent infections — and whether routine blood tests are right for you.