Levothyroxine and Vitamin Supplements

When you have hypothyroidism, your thyroid gland can't make enough of the hormones your organ systems need to function properly. Many people rely on levothyroxine to control this condition, and avoiding vitamin supplements containing certain minerals is crucial for levothyroxine to work properly.

Levothyroxine can help control hypothyroidism. (Image: skaman306/Moment/GettyImages)

Vitamin Supplements to Avoid

The 13 essential vitamins include vitamins A, C, E, D, K and the eight B vitamins. No studies report that vitamins interact with or affect the absorption of levothyroxine, the synthetic hormone used to treat hypothyroidism. Taking a specific supplement that contains only a single vitamin, such as vitamin D, or one that contains multiple vitamins, such as B complex, should not interfere with how your medication works.

However, one B vitamin, biotin, can affect blood test results. Your doctor will perform blood tests to diagnose hypothyroidism and to monitor your blood levels for thyroid stimulating hormones. It is important to let your doctor know if you are taking any type of supplement that may contain biotin.

Problems With Minerals

Taking a vitamin supplement that also contains minerals, as many do, does poses a problem. The minerals calcium, iron, magnesium and aluminum interfere with how your body absorbs levothyroxine, as well as other thyroid hormone replacement medicines and thyroid supplements. To prevent this, you should not take supplements containing these minerals within four hours of taking your medication, the Food and Drug Administration (FDA) advises.

Iodine deficiency can cause hypothyroidism; however, deficiency in this mineral is rare in the United States since it's often added to salt and other foods, reports the Mayo Clinic. Some multivitamins contain iodine, but supplementation won't help your condition unless you have low blood levels.

For people who have abnormal thyroid glands, taking too much iodine can worsen hypothyroidism. As with any supplement, it's important to ask your doctor whether a vitamin supplement containing iodine is safe for you to take.

Foods and Levothyroxine Absorption

In addition to minerals, certain foods may affect the way your body uses levothyroxine. Any foods that are high in calcium and iron should be avoided within one hour before or after taking medication, according to the FDA. Calcium-rich foods include:

  • Milk
  • Cheese
  • Yogurt
  • Ice cream
  • Cottage cheese
  • Sardines canned with bones
  • Salmon canned with bones
  • Canned shrimp
  • Collard greens
  • Broccoli rabe
  • Kale
  • Soy beans
  • Fortified foods, such as cereal, breads, plant milks and orange juice

Iron-rich foods to avoid include:

  • Fortified foods
  • Oysters
  • White beans
  • Dark chocolate
  • Beef liver

Additionally, the Mayo Clinic advises avoiding taking levothyroxine at the same time as walnuts, cottonseed meal, soybean flour and any fiber-rich foods including fruits, vegetables, grains, nuts, seeds and legumes. According to the U.S. Library of Medicine's publication MedlinePlus, grapefruit and grapefruit juice may also affect the medication's function. Because so many foods can affect levothyroxine, it's recommended that you take it on an empty stomach.

Interactions With Medications

The list of potential drug interactions is lengthy. A partial list provided by MedlinePlus includes:

  • Amiodarone (Nexterone, Pacerone)
  • Androgens including nandrolone and testosterone
  • Certain antacids containing aluminum, calcium or magnesium
  • Anticoagulants or blood thinners heparin or warfarin
  • Beta-blockers, such as metoprolol, propranolol or timolol
  • Medications for cancer, such as asparaginase, fluorouracil and mitotane
  • Carbamazepine
  • Clofibrate
  • Corticosteroids, such as dexamethasone
  • Cough and cold medications
  • Weight loss medications
  • Digoxin
  • Medications containing estrogen such as hormone replacement therapy or hormonal contraceptives, for example, birth control pills, patches, rings, implants or injections
  • Furosemide
  • Insulin or other medications to treat diabetes
  • Maprotiline
  • Mefenamic acid
  • Methadone
  • Orlistat
  • Phenobarbital
  • Phenytoin
  • Proton pump inhibitors, such as esomeprazole
  • Lansoprazole
  • Omeprazole
  • Rifampin
  • Sertraline
  • Simethicone
  • Sucralfate
  • Tamoxifen
  • Tyrosine kinase inhibitors, such as cabozantinib
  • Tricyclic antidepressants, such as amitriptyline

Tell your doctor if you are taking any medications on this list that your doctor did not prescribe. Some of these medications are necessary for certain conditions; rather than stopping the medication, your doctor can adjust your levothyroxine dosage and monitor you for side effects.

Tip

Safety warning: The problem with taking any supplement is that you can't be absolutely sure what it contains. The FDA doesn't regulate supplements the same way it does foods. Supplements can be adulterated or mislabeled, but the FDA can take action only after the supplement has reached the market — and that's only if the FDA finds out about a potential problem.

Do You Need Vitamin Supplements?

When you're taking a medication like levothyroxine that is so crucial for your body to function properly, it might be better to avoid supplements altogether. Although you may need to supplement with single nutrients to prevent or treat a deficiency if your doctor advises it, taking a daily multivitamin likely isn't necessary anyway. Existing research doesn't show that taking a vitamin supplement is effective for preventing disease.

For example, a review of research published in Annals of Internal Medicine in December 2013 that analyzed results of studies involving nearly 400,000 participants did not find any significant evidence of a beneficial effect of vitamin and mineral supplements on heart disease and cancer.

Another study published in Annals of Internal Medicine in December 2013 concluded that long-term supplementation with a multivitamin had no effect on the cognitive health of the 6,000 male participants enrolled in the trial.

Healthy Diet for Hypothyroidism

Aside from avoiding certain foods close to the time when you take levothyroxine, there isn't a specific diet for hypothyroidism, according to Mayo Clinic. However, your diet is of supreme importance, because it can bolster your health and wellbeing and make taking a vitamin supplement unnecessary.

A healthy diet looks the same, whether you have hypothyroidism or not. Most important, you should avoid non-nutritive junk food and drinks that are high in sugar and made with refined grains. Fatigue and weight gain are prominent symptoms of hypothyroidism; ditching these unhealthy foods can help you control your calorie intake and prevent blood sugar spikes and crashes that often result from eating heavily processed foods.

One way you can naturally start to reduce your consumption of these unhealthy foods is to add more nutritious foods to your diet. This often effectively "crowds out" junk foods. Focus on eating more fresh fruits and vegetables, lean meat, poultry, fish, eggs, beans, low-fat dairy, nuts and seeds.

Just be careful not to eat foods high in iron, calcium or magnesium within one hour of taking your medication. While you may have to take levothyroxine for life, you can dramatically improve your overall health and wellbeing with a nutritious diet.

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