In the recent series of Memos on thyroid issues, I explained what you need to know about levothyroxine, the medication prescribed for an underactive thyroid gland. New research highlights a key factor in ensuring its effectiveness.

Researchers examined a dietary supplement to see what impact it would have on absorption of levothyroxine. They found that chromium picolinate reduced the absorption of the drug in subjects who took a high level of levothyroxine.

If chromium picolinate, typically used in weight loss supplements, interferes with high levels of the drug, it could impact lower doses even more; less would be available to be absorbed. If not as much of the drug is absorbed, it will not be as effective.

If you’re trying to lose weight, the last thing you want to do is lower your metabolic rate, so what should you do if you take both levothyroxine and chromium? The researchers recommended that people taking the medication be warned to take it at a different time from the supplement; four hours is the time frame. Take your levothyroxine as soon as you get up—that’s when you should be taking it anyway—and begin the supplement with lunch and throughout the rest of the day, depending on how much you take.

What are you prepared to do today?

Dr. Chet

Reference: Thyroid. 2007 Aug;17(8):763-5.