A:

To treat low thyroid function, you need a specific amount of thyroid hormone supplement. Getting the right amount can be tricky if you take your thyroid pills at the same time that you eat food or take other medicines.

A number of medicines can cause your body to digest and absorb thyroid medicine less efficiently. These include:

• Iron supplements
• Calcium carbonate supplements
• Anti-acid medicines

Some medicines attach (bind) to the thyroid medicine. This makes it difficult for your body to absorb the thyroid pills.

In other cases, the problem relates to stomach acid. To be absorbed efficiently, thyroid medicine needs to be exposed to stomach acid. Starting or stopping an antacid medicine might mean you have to adjust a dose of your thyroid pills. Some people don’t realize that their calcium supplements might neutralize stomach acid. This is especially true for calcium carbonate (the main ingredient in "TUMS").

Calcium in food is not specifically known to be a hazard, but food in general does seem to change how efficiently you absorb thyroid medicine. Pharmacists recommend that you take your thyroid medicine on an empty stomach. Take your pills at least 30 minutes before you eat. If you take a calcium supplement, it will be hard for you to absorb your thyroid medicine for the next four hours.