One of the things that many people don’t know is that coffee can impair the absorption of thyroid medications and therefore needs to be spaced out from thyroid medications!
Food, in general, can impair the absorption of thyroid hormones, so this is why it’s always recommended to take thyroid hormones on an empty stomach, with a glass of water.
A person with normal digestive function can take thyroid medications 15-30 minutes prior to breakfast and have the medications be well absorbed, but some people may need to postpone breakfast by a minimum of 60 minutes after taking thyroid medications for proper absorption. One suggestion is to keep your thyroid medications at your bedside, so you can take them as soon as you wake up.
As far as coffee and thyroid meds go, Italian researchers found that their first-thing-in-the-morning-espresso-loving patients did not absorb their thyroid medications correctly. This is because coffee lowers the intestinal absorption of both inorganic and organic compounds, and seems to physically interact with thyroid medications.
In an Italian study, one person who was drinking espresso within 10 minutes of thyroid medications had a consistently elevated TSH between 13 μIU/mL and 18 μIU/mL. The same person, on the same dose of medication, was later made to wait one hour to have her coffee, and took her medication with a full glass of water instead. With this new change, her TSH was now testing between to 0.03-0.1μIU/mL every time she had it tested.
While most of the studies on coffee and thyroid hormone absorption have been done with levothyroxine, anecdotally, people taking T3 and natural desiccated thyroid hormones can also have a problem with absorbing them if they’re taking them with coffee.
Other foods that may interfere with thyroid medication absorption include soy, dairy products, grapefruit juice, walnuts, and dietary fibre.