Most people with hypothyroidism can safely donate blood. There is no evidence that someone with thyroid disease who donates blood is at risk of adverse events.

Before opting for blood donation, a person with hypothyroidism can speak with a healthcare professional for further advice.

People undergoing testing to determine the cause of their hypothyroidism may have to wait for those results before donating blood. For example, if cancer is causing low thyroid levels, donation is not advisable.

People with hypothyroidism taking thyroid replacement hormones, such as thyroxine or levothyroxine (Synthroid), may sometimes need to wait before donating blood.

If a person is starting levothyroxine for the first time, they have to wait 8 weeks before donating blood. Those already taking the medication can donate blood if their dose has not changed in the last 4 weeks.

Anyone who has taken anti-thyroid medications in the last 2 years may not be able to donate blood.

Anyone who has received radioactive iodine treatment for their thyroid condition — usually for hyperthyroidism, not hypothyroidism — has to wait 6 months before donating blood.

Every person who wants to donate blood has to meet certain criteria. According to American Red Cross guidelines, a person must:

  • be at least 16 years old (some states may require parental consent)
  • weigh at least 110 pounds (about 50 kilograms)
  • not be currently ill or pregnant
  • not have low iron levels
  • not have recently traveled to an area where malaria is present

People with hypothyroidism who want to donate blood and have concerns can speak with a healthcare professional or local donation center about eligibility.