How to Take Your Thyroid Drug Correctly

With food? Away from other meds? Are goitrogens like kale off limits?

Portrait of mature woman looking at pill bottles.
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Hypothyroidism is a condition where the thyroid cannot make sufficient thyroid hormone for the body's needs. The goal of thyroid hormone treatment is to replace the function of the thyroid, get necessary thyroid hormone to all the cells of your body, and improve your sense of energy and well-being. The most common drug prescribed to treat the disease is levothyroxine (which is synthetic T4 and goes by Synthroid and other names), though some people feel much better taking T3, such as in the form of Cytomel, alone or in combination with T4—or natural desiccated thyroid, such as Armour Thyroid.

It is critical to take your thyroid hormone correctly, as your body is missing this hormone and requires it in order to carry out every function. Some medications interact with thyroid hormone, and some substances and behaviors prevent its full absorption. Here's a review of some of the current thinking, though it is crucial to also read the patient insert that comes with your prescriptions, and always talk to your doctor and pharmacist regarding specific questions.

Don't Take Your Thyroid Medication with Food

Food may delay or reduce the absorption of many drugs, including thyroid hormone. Food may affect absorption of the drug you're taking by binding with it, by decreasing access to absorption sites, by altering the rate at which it dissolves, or by changing the stomach's pH balance. This is why many doctors recommend that for best absorption of your thyroid hormone, you should take it first thing the morning, on an empty stomach, one hour before eating.

However, if you cannot take it this way, consistency becomes the key. If you're going to take your thyroid hormone with food, take it every day with food, consistently. If you've changed from taking it on an empty stomach, then around six to eight weeks after you start taking it with food, you should have another TSH test to ensure you're receiving the proper amount of thyroid hormone.

Taking the drug with food might inhibit absorption somewhat, but this safety check will make sure your dosage gets tweaked if it needs to be changed slightly. But again, consistency. Don't take it some days with food, some days without, or you're sure to have erratic absorption, and it will be harder to regulate your TSH levels.

Don't Be Afraid of Fiber—But Know It May Inhibit Absorption

Given that many people on thyroid replacement therapy are fighting an additional battle to lose weight, high fiber diets are also an issue. Anything that affects your digestion speed or speed of absorption of items into the stomach can have an effect on your absorption of thyroid hormone. Since high-fiber diets can, ahem, speed things up a bit, they are known to inhibit absorption for some people. So, should you forget about eating high-fiber?

Absolutely not! Since the benefits of fruits, vegetables, and a high-fiber diet are well-known, again, the issue here is consistency. If you are already eating a high-fiber diet regularly and have regular TSH testing done, your dosage level is appropriate for you, given your diet. If you are starting a new regimen of eating high-fiber, plan to get thyroid testing around six to eight weeks after you change your diet, to make sure you're receiving the proper amount of thyroid hormone.

But be consistent. Don't jump around, or you'll have erratic absorption, and that can wreak havoc on TSH levels...AND how you feel! But again, taking your thyroid hormone first thing a.m. on an empty stomach, and waiting at least an hour to eat, will ensure maximum absorption, whatever your diet is!

Be Careful About Taking Supplemental Iodine or Kelp

While some herbalists and vitamin proponents recommend iodine tablets or kelp supplements (which are high in iodine) for people with thyroid problems, you need to be extremely careful about any decision to take iodine or kelp supplements if you are on thyroid hormone replacement therapy.

The thinking behind taking iodine or kelp is that in many parts of the world, goiters and thyroid disease are related to iodine deficiency. In the U.S. and other developed countries, iodine deficiency is not very common anymore, due to the addition of iodine to salt (iodized salt) and other food products. In fact, the most common forms of thyroid disease found in the U.S.—autoimmune thyroid diseases like Graves' Disease or Hashimoto's Thyroiditis—have nothing to do with iodine deficiency at all. Actually, thyroids are extremely sensitive to iodine, and you need to be careful about adding too much iodine to the diet as it can irritate or aggravate the thyroid. Most doctors say not to worry about some iodized salt or the iodine present in a food item such as an occasional sushi dinner. But even alternative nutritional doctor Stephen Langer, author of Solved: The Riddle of Illness, the follow-up book to Broda Barnes' Hypothyroidism: The Unsuspected Illness, advises against taking iodine or kelp supplements for people with autoimmune thyroid disease.

If You Still Have a Thyroid, Don't Eat "Goitrogenic" Foods in Excess

Goitrogenic foods like brussels sprouts, rutabaga, turnips, cauliflower, African cassava, millet, babassu (a palm-tree coconut fruit popular in Brazil and Africa) cabbage and kale can act like the antithyroid drugs propylthiouracil and methimazole in disabling the thyroid function, so they should not be eaten in large amounts by someone on thyroid hormone replacement who still has a thyroid. However, these foods are very healthy, and eating them in moderation is fine. It's thought that the enzymes involved in the formation of goitrogenic materials in plants can be destroyed by cooking, so thorough cooking may minimize goitrogenic potential.

Take Antacids, Calcium, and Iron Away from Your Thyroid Medication 

Antacids—like Tums or Mylanta, in liquid or tablet forms—may delay or reduce the absorption of thyroid drugs, and therefore, should be taken at least two hours apart from when you take your thyroid hormone.

Like antacids, calcium can interfere with the absorption of thyroid drugs. You should take calcium at least two to three hours apart from taking your thyroid hormone. The same holds true for calcium-fortified orange or apple juice. You should not take your thyroid hormone at the same time as calcium-fortified juice.

And finally, iron, whether alone or as part of a multivitamin or prenatal vitamin supplement, interferes with thyroid hormone absorption. You should not take your vitamins with iron at the same time as your thyroid hormone and should allow at least two hours between taking them.

Check the Labels of Cold Medicines and Decongestants

Most packages of over-the-counter cough and cold medicines and decongestants say: "Do not take if you have one of the following..." and then goes on to list thyroid disease. While you should always check with your doctor, it's generally understood that this warning is more applicable for people with hyperthyroidism (overactive thyroid) than hypothyroidism (underactive thyroid). Because these drugs contain stimulants, the logic is for someone with hyperthyroidism to avoid adding even further stimulation or strain on the heart from these drugs. That said, some people with hypothyroidism do find that they become sensitive to ingredients like pseudoephedrine, what you'd typically find in Sudafed or other decongestants. Some doctors will recommend you try only a partial dose, and see if you have a reaction, and only then try to work your way up to the normal dose and see if it bothers you.

If You're On Synthetic Estrogen, Talk to Your Doctor

Women taking estrogen (either as hormone replacement -- i.e., Premarin -- or in birth control pills) may need to take more thyroid replacement hormone. Estrogen increases the body's production of a blood protein that binds thyroid hormone to it, making it inactive. For women without thyroids, in particular, this can cause a need to increase the dosage level slightly, as there is no thyroid to compensate. After beginning any estrogen therapy, a woman should always have TSH tested to see if the estrogen is having an impact on overall TSH and thyroid function and might require a dosage adjustment.

Know These Prescription Drugs that May Interact With Thyroid Hormone

Antidepressants. Use of tricyclic antidepressants at the same time as thyroid hormones may increase the effects of both drugs, and may accelerate the effects of the antidepressant. Be sure your doctor knows you are on one before prescribing the other.

Insulin. Insulin and the similar oral hypoglycemic drugs for diabetes can reduce the effectiveness of thyroid hormone. Be sure your doctor knows you are on one before prescribing the other. If you're on insulin or an oral hypoglycemic, you should be closely watched during the initiation of thyroid replacement therapy.

Cholesterol-Lowering Drugs (Cholestyramine or Colestipol -- Colestrol, Questran, Colestid). These cholesterol-lowering drugs bind thyroid hormones, and a minimum of four to five hours should elapse between taking these drugs and thyroid hormones.

Anticoagulants ("Blood Thinners").Anticoagulant (blood thinning) drugs like Warfarin, Coumadin or Heparin can on occasion become stronger in the system when thyroid hormone is added to the mix. Be sure to mention to your doctor if you are on one or the other, and a new prescription is added.

Note: The above is NOT a complete list of all drugs that can interact with thyroid medicines. Talk to your pharmacist or doctor for more information.

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