Coffee has been added to the list of things that interfere with absorption of thyroid hormone. That's the list of things that you shouldn’t take along with thyroid hormone keeps growing. Most simply hinder absorption of the drug from the digestive tract and effectively reduce the dose that gets into your blood. This isn’t a big problem is you only eat these foods rarely; if for one day you don’t absorb all of your thyroid dose, it’s not a big deal. If you eat the same foods every single day, it’s also not a big deal because you’ll adjust the amount of medicine you take to a slightly higher dose and compensate. The problem shows up with food or other medications that people will start to take regularly. This can throw of your dose requirements.

Take coffee. This may be a problem for many people with hypothyroid function who are taking replacement hormone.
If these people are under treated they feel really tired. If they are also vitamin B-12 deficient, the feel really, really tired.

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Tired people drink coffee. According to a paper published this past March, coffee decreased the amount of thyroid hormone absorption by about a third. Instead of tired, these people will start to feel exhausted. So, they drink more coffee and they absorb even less of their hormone dose. It’s a vicious cycle. The trick is to take thyroid hormone first thing in the morning on an empty stomach, at least 30 minutes before eating anything.

Coffee isn’t the first thing discovered to interfere with thyroid hormone. Back in 1992 both hydroxide antacids and the iron supplement ferrous sulfate were reported to interfere. In 2000 a report in JAMA added Calcium carbonate to the list. And soy protein shakes in 2001. And the drug Raloxifene was added in 2003. Then chromium picolinate in 2007. And now, coffee.

Some patients just lie and tell their doctors that they took their medicine when they didn’t. But not our patients. There are some foods, namely cabbage that are well known to decrease thyroid hormone production and cause goiters if eaten in large enough quantities, but that’s not what I’m writing about here.

Thus the general direction given to all patients taking supplemental thyroid hormone to always take it alone without food or other medication. You just don’t know what’s going to mess things up.

When a patient who is taking thyroid hormone does well initially and then it seems the drug stops working, the first thing to rule out is interference from something else they are taking.

A 2007 paper tells us that taking thyroid hormone at bedtime works much better than taking it in the morning. For some reason the hormone is better absorbed at night and reaches greater blood concentrations than when taken in the morning.


Thyroid. 2008 Mar;18(3):293-301.
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Arch Intern Med. 1992 Jan;152(1):183-4.Links
Evidence for interference with the intestinal absorption of levothyroxine sodium by aluminum hydroxide.
Sperber AD, Liel Y.

Ann Intern Med. 1992 Dec 15;117(12):1010-3.Links
Ferrous sulfate reduces thyroxine efficacy in patients with hypothyroidism.
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JAMA. 2000 Jun 7;283(21):2822-5.
Effect of calcium carbonate on the absorption of levothyroxine.
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docr Pract. 2001 May-Jun;7(3):193-4.
Use of soy protein supplement and resultant need for increased dose of levothyroxine.
Bell DS, Ovalle F.

Arch Intern Med. 2003 Jun 9;163(11):1367-70.
Raloxifene causing malabsorption of levothyroxine.
Siraj ES, Gupta MK, Reddy SS.

Thyroid. 2007 Aug;17(8):763-5.
New medications which decrease levothyroxine absorption.
John-Kalarickal J, Pearlman G, Carlson HE.

Presse Med. 2007 Oct;36(10 Pt 1):1390-4. Epub 2007 Apr 18.
[L-thyroxine pseudomalabsorption: a factitious disease]
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Clin Endocrinol (Oxf). 2007 Jan;66(1):43-8.
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Author's Bio: 

Jacob Schor ND FABNO has practiced naturopathic medicine in Colorado since 1991, served as president of the Colorado Association of Naturopathic Physicians form 1992-1999. He was trained at National College of Naturopathic Medicine in Portland Oregon and maintains a license as a naturopathic physician in Oregon. He is currently serving his second term on the board of directors of the Oncology Association of Naturopathic Physicians. He has been awarded Fellow status by the American Board of Naturopathic Oncologists.

A great many additional articles written by Dr. Schor are available for free on his website