There is a problem, however, when coffee drinkers take their prescription thyroid tablets along with their morning coffee or espresso. Several studies have found that having coffee or espresso at the same or shortly after taking levothyroxine tablets can significantly lower the absorption of the thyroid medication.
In one study published in the journal Thyroid, the rise of T4 -- a reflection of absorption of the medication -- was reduced by 25%, and drops of as much as 57% were seen in other patients in that study. Overall, the Thyroid journal study showed that the reduction typically ranged from 23% to as much as 55%.
Consistently, researchers have found that for patients taking levothyroxine tablets, absorption is affected by drinking coffee and espresso within an hour of taking the thyroid drugs. The ability to reach targeted thyroid levels is impaired if a thyroid patient does not wait sixty minutes after taking the levothyroxine before drinking coffee or espresso.
What the Study Did Not Evaluate
It's important to note that there are a number of things the study did not evaluate:
- The study did not differentiate between regular and decaffeinated coffee.
- The study did not test the effect of coffee on thyroid hormone replacement medications beyond levothyroxine tablets. So we do not have any scientific conclusions regarding synthetic T3 (i.e., Cytomel), and natural desiccated thyroid drugs like Nature-throid and Armour Thyroid. The study also did not include antithyroid drugs (like methimazole or PTU), which are used to treat hyperthyroidism.
- The study did not evaluate the effects of caffeinated or herbal teas.
So scientifically, we don't have any conclusions about whether the same negative effects would be seen with drinking decaf coffee, or caffeinated tea, or other beverages, within an hour of taking levothyroxine.
We also do not have any conclusions regarding whether the cautions regarding coffee and espresso also apply to other thyroid hormone replacement drugs besides levothyroxine, or to antithyroid drugs.
Implications for Thyroid Patients
The recommendations by researchers are clear: wait at least sixty minutes after taking levothyroxine before drinking coffee or espresso.
And if that is not possible, then patients may want to talk to the doctor about taking levothyroxine medication at night. Some studies have shown that taking levothyroxine at bedtime may improve absorption. It also allows for a thyroid patient to have a morning cup of coffee without concern for interference with thyroid medication.
You may also ask your doctor about Tirosint as a substitute.
It's important to note, however, that any time you are finding it difficult to regulate your thyroid function while taking any thyroid hormone replacement drug, experts recommend that you take your medication consistently, ideally in the morning, at least an hour before any food or drink besides water, and at least three or more hours apart from any supplements, juices or foods that contain iron, calcium, or fiber.
Benvenga, S. et. al. “Altered Intestinal Absorption of L-Thyroxine Caused by Coffee.” Thyroid. Vvolume 18 Issue 3, pages 293-301. March 2008 Abstract.
Mazzaferri, MD MACP, Ernest. "Thyroid Hormone Therapy," Clinical Thyroidology for Patients: Summaries for Patients from Clinical Thyroidology. August 2008 Vol 1, Iss 1. Online
Sindoni, Alessandro et. al. "Case Report: Coffee Impairs intestinal Absorption of Levothyroxine: Report of Additional Cases," Hot Thyroidology, Article 5/09, Online (PDF)