5 supplements you shouldn’t take if you have hypothyroidism, according to experts

Certain supplements may interfere with thyroid medication or blood tests. Here’s what experts recommend avoiding and what to do instead.

Key Points

• Some supplements, like iron and calcium, may block the absorption of hypothyroidism medication.
• Others, like biotin, kelp and animal thyroid, may affect blood tests or thyroid health.
• Before taking these or any other supplements, speak with your health care provider.

Hypothyroidism occurs when the thyroid gland doesn’t produce enough thyroid hormone. If you have hypothyroidism, you need to be especially cautious with supplements, particularly if you take medication. “Taking thyroid replacement medications can have interactions with certain supplements which might affect how the body utilizes the medication,” says Alyssa Smolen, M.S., RDN. Alternatively, some supplements may affect thyroid-related lab tests or impair your overall thyroid health.

To fully understand why some supplements can spell trouble for people with hypothyroidism, it helps to have a little thyroid 101. Your thyroid gland is a small gland in your neck that helps regulate metabolism, energy levels and many other essential body functions. “When [thyroid hormone] levels are low, everything slows down,” says endocrinologist Andres Splenser, M.D. This can result in symptoms like fatigue, weight gain, feeling cold and changes in mood or cognition.

The most common cause of hypothyroidism is autoimmune thyroid disease, particularly Hashimoto’s thyroiditis, in which the immune system mistakenly attacks the thyroid gland, reducing its ability to produce thyroid hormones.

Treating hypothyroidism often involves thyroid hormone replacement medication, usually levothyroxine. So, the last thing you want is to take a supplement that will interfere with your medication’s absorption or throw off the results of your lab work, especially these.

1. Iron

Iron supplements are commonly used to treat iron-deficiency anemia, but they can interfere with the thyroid medication levothyroxine if taken too close together. That’s because iron can bind to levothyroxine, blocking its absorption in the small intestine, explains Emer Delaney, R.D.

Ideally, levothyroxine should be taken first thing in the morning on an empty stomach one hour before breakfast. But if you are taking an iron supplement, you may have to space them even farther apart. “If you intend to take an iron supplement, the advice would be to take it at least four hours after medication,” she says. 

2. Calcium

While calcium is essential for bone health, taking calcium supplements at the same time as levothyroxine can negatively affect how well your thyroid medication works. “Calcium is another supplement that people need to be very careful of,” cautions Delaney. “Similar to iron, it binds to thyroid medication in the gut, prevents it from absorbing effectively and it can reduce [levothyroxine] bioavailability by up to 25%.”

“Any supplement or medication containing calcium or iron should be separated from thyroid hormone medication because they can impair its absorption,” says endocrinologist Chhaya Makhija, M.D. “This interference may result in abnormal thyroid hormone levels on blood tests or symptoms that appear consistent with inadequate thyroid hormone.” 

Like iron, calcium should be taken at least four hours after levothyroxine.

3. Biotin

Biotin is a B vitamin often marketed for hair, skin and nail health. While it doesn’t directly affect thyroid hormone levels, research shows it can interfere with thyroid lab tests and lead to inaccurate results.

“Laboratory assays used to measure thyroid hormones can be affected by excess biotin, which may result in falsely abnormal thyroid hormone levels in the blood test,” explains Makhija. For this reason, the American Thyroid Association recommends avoiding biotin supplements for at least two days before thyroid testing. However, always confirm this with your health care provider first.

4. Kelp or High-Iodine Supplements

Kelp supplements are often touted as a natural way to support thyroid health because they contain iodine. While some iodine is essential for proper thyroid function, too much of it can worsen thyroid problems.

“If someone has hypothyroidism—especially autoimmune hypothyroidism—they do not require additional iodine supplementation beyond what is naturally available in their food,” says Makhija. “Excessive iodine may sometimes contribute to thyroid inflammation.”

Most of us get adequate amounts through food. Since iodine levels in kelp supplements can vary so widely, experts recommend avoiding these products unless you’re specifically told to take them by a clinician.

5. Thyroid Support Supplements

Some supplements marketed for thyroid support contain animal thyroid or glandular extracts. While these may sound like a more natural way to treat a slow thyroid, experts caution against them. “Products containing animal thyroid extract or animal glandular extracts may contain active thyroid hormones and can interfere with proper thyroid function and management,” says Makhija.

Because dietary supplements are not regulated as strictly as prescription medications, these supplements may contain inconsistent or unlisted ingredients. This can make it challenging for clinicians to help people with hypothyroidism manage their symptoms.

Strategies to Support Thyroid Health Without Supplements

To keep your thyroid as healthy as possible, follow these expert-backed strategies.

• Take thyroid medication correctly: “The safest and most effective evidence-based way to support thyroid health is for people to take their prescribed medication, i.e., levothyroxine, correctly and consistently,” says Delaney. For optimal absorption, experts recommend taking levothyroxine on an empty stomach, 30 to 60 minutes before breakfast, and at least four hours after products containing iron or calcium.

• Follow a balanced eating plan: There is no proven eating plan to reverse hypothyroidism, but filling your plate with lots of whole, nutritious foods can give you the nutrients your body needs to support thyroid health, especially iodine, zinc, iron and vitamin D.

• Stay active: When you have a slow thyroid, exercise might be the last thing you feel like doing. But research reveals that exercise can help improve many aspects of health that can decline with hypothyroidism, such as mood, muscle health and cardiovascular health. Just five 30-minute walks per week can help you meet the weekly recommended 150 minutes of exercise.

Our Expert Take

While supplements may seem like a quick way to support thyroid health, certain supplements can interfere with thyroid medication or thyroid lab tests. Experts caution people with hypothyroidism to be careful with supplements containing iron, calcium, biotin, kelp or animal thyroid extracts.

Instead of relying on supplements for thyroid health, safer approaches include taking prescribed thyroid medication correctly, eating plenty of whole, nutritious foods and staying physically active. That said, you can take iron and calcium supplements as long as you take them four hours after your thyroid medication. However, if you are considering any new supplement, speak with your health care provider first to make sure it’s right for you.

Read the original article on EatingWell