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6 Things That Can Affect Your Thyroid Medication

Learn about medications, supplements, and foods that can impact how well your body absorbs thyroid medication.
6 Things That Can Affect Your Thyroid Medication
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The thyroid is the butterfly-shaped gland at the base of the neck. As part of the endocrine system, the thyroid produces hormones that regulate the body’s energy use, among other vital functions.

Hypothyroidism is a condition in which the thyroid gland produces too little thyroid hormone. Our bodies require thyroid hormones for essential processes such as growth and metabolism, energy production, heart rate control, and digestive function.

Without adequate levels of thyroid hormone, you can suffer from several unpleasant and common symptoms or conditions, including:

  • Constipation
  • Weight gain
  • Puffy face
  • Hoarseness
  • Muscle weakness
  • Elevated blood cholesterol level
  • Tender, achy, or stiff muscles
  • Painful, stiff, or swollen joints
  • Heavier than usual or irregular menstrual periods
  • Thinning hair
  • Slowed heart rate
  • Depression
  • Impaired memory
  • Reduced sexual desire and sexual function

Most people with an underactive thyroid take a daily thyroid hormone replacement medication. The right type and dose of thyroid medication can help improve these symptoms and your overall health and quality of life.

How do thyroid hormone medications work?

Thyroid hormone replacement medications are synthetic (lab-made) versions of the hormones naturally made by the thyroid gland. These medications work by supplementing or replacing the amount of thyroid hormone your thyroid can no longer make.

Your thyroid makes and releases two thyroid hormones—T4 (thyroxine) and T3 (triiodothyronine). The thyroid gland produces primarily T4, which is inactive when released. Once in the bloodstream, specific cells in the body convert T4 to T3, the active form. For your cells to use thyroid hormone, it must be in the T3 form.

Thyroid hormone medications mimic the actions of natural thyroid hormones. There are three types of thyroid medications your provider can prescribe to help optimize thyroid function:

  • Synthetic T4: These medications contain T4 only. Levothyroxine falls into this group and is the most commonly prescribed medication to help manage hypothyroidism. Your body absorbs levothyroxine into the bloodstream, which is then converted to T3 in specific cells—just like the natural process described above.
  • Synthetic T3: These medications only contain T3 and can be used alone or in combination with a T4-only medication. Your body quickly absorbs T3 into the bloodstream; your cells can use it immediately since it is already active. This can provide immediate relief of hypothyroid symptoms. However, it doesn’t help build up T4 reserves in the body, so the effects may be short-lived.
  • Natural T4 and T3 combination: Desiccated thyroid medications -- also known as natural desiccated thyroid, or NDT -- are made from the thyroid gland of animals, usually pigs. Because of this, desiccated thyroid medications have T4 and T3 in quantities similar to those released by a human thyroid. There is a drawback - getting the same amount of thyroid hormone in each tablet is unlikely.

Suppose you feel your thyroid symptoms are not improving or are worsening while taking your prescribed thyroid medication. In that case, you should check to see if anything in your daily routine is affecting the absorption of your medication. Below, we will examine six factors that can interfere with your thyroid medication.

1. Taking your medication with food

Most thyroid medications need to be taken on an empty stomach to enhance the body’s absorption. The recommendation is to take your dose of thyroid medication 30 to 60 minutes before your first meal of the day. You can also take it before bedtime if your last meal of the day was 2 hours prior.

Certain foods and nutrients, like calcium and iron, as well as medications, can interfere with the absorption of levothyroxine. To maintain thyroid hormone balance, you should give your body the best chance to absorb equal amounts of medication daily.

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2. Inconsistent medication schedule

Your body relies on a consistent level of thyroid hormones to function correctly. Because of this, you should take your thyroid medication at the same time every day.

Frequently changing when you take your thyroid medication or skipping doses may change how you absorb the medication, resulting in fluctuations in your thyroid hormone levels. In turn, you may start to notice hypothyroid symptoms reappearing. It is important to remain consistent in taking your thyroid medication at the same time every day. However, T3-only and T4/T3 combination medications may be more sensitive to inconsistencies.

Make taking your medication part of your daily routine—i.e., take your medicine before you wash your face or comb your hair. If you miss your scheduled time, take your medication as soon as you remember and then resume your regular dosing schedule. If it is already close to your next dose, skip the missed dose unless your provider tells you otherwise. It is best not to take multiple doses in one day to make up for missed ones.

3. Switching between medications

Each thyroid hormone medication brand is slightly different despite sharing the same active ingredient. Even minor differences in the pill makeup could influence the way your body absorbs and uses the drug.

Differences in pill makeup can include:

  • Coatings
  • Lubricants
  • Fillers or diluents
  • Preservatives
  • Coloring agents
  • Sweeteners
  • Flavoring agents

Common fillers for tablets and capsules include cornstarch or sugars like glucose and sucrose. In liquid formulations, glycerin and water dissolve or suspend active ingredients. These non-active ingredients help ensure that a drug has consistent and reproducible quality.

Sometimes, switching brands may be necessary if your preferred one is unavailable. If you switch brands, it’s important to let your provider know. They may want to retest your thyroid every four to six weeks and adjust your dosage until your levels are stable.

4.Taking other medication or supplements at the same time

Before starting thyroid replacement hormones, talk to your pharmacist or healthcare provider to see if any other medicines or supplements you take may interact with your thyroid medication.

Many supplements can prevent your body from fully absorbing your thyroid medication. These include:

  • Calcium supplements
  • Iron supplements
  • Supplements that contain aluminum hydroxide
  • Chromium
  • Vitamin C

Beware of hidden sources of calcium and aluminum hydroxide. Apart from calcium supplements, many over-the-counter (OTC) antacids often have one or both of these elements as a component of the medication. Other OTC and prescription medications that can interfere with the absorption of your thyroid medication include:

  • Proton pump inhibitors (PPIs), such as omeprazole or pantoprazole
  • Orlistat
  • Sevelamer
  • Cholestyramine
  • Sucralfate

A general rule of thumb is to not take supplements or medications within 2 to 4 hours after taking your thyroid medication. However, there may be specific recommendations based on the medication or supplement. Ask your pharmacist or healthcare provider how long you should wait to take other supplements and medicines after taking your thyroid medication.

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5. Taking your medication with liquid other than water

Believe it or not, taking your thyroid medication with a liquid other than water can negatively influence its absorption. Liquids that are known to affect thyroid medication absorption include:

  • Cow’s milk
  • Soy-based liquids
  • Coffee (including decaf)
  • Fruit juices such as grapefruit, orange, and apple
  • Calcium-fortified juices
  • Mint tea
  • Alkaline water

Plant-based milk alternatives such as rice, oat, coconut, or almond milk have a different calcium and protein concentration than cow’s milk. It is unknown if plant-based milk alternatives affect the absorption of thyroid medications. Because of this, it is best to avoid taking your thyroid medication with plant-based milk.

6. Eating a diet rich in fiber

Fiber is an essential part of a thyroid-healthy diet. Fiber has many benefits, including:

  • Maintaining a healthy gut microbiome
  • Controlling weight
  • Relieving constipation (a troublesome symptom for people with hypothyroidism)
  • Lowering your risk for heart disease and diabetes

But, eating too much fiber in your diet may interfere with thyroid hormone medication absorption. To allow time for optimal absorption, eat fibrous foods, like whole wheat bread or granola, at least one hour before or after taking your thyroid medication.

A note from Paloma Health

Finding the best thyroid treatment for you is essential and can take some time. Each person with thyroid disease is unique, with individual sensitivities, and our bodies will not all react the same way to a specific medication or dosage.

Here at Paloma Health, we want you to feel your best! We specialize in testing your thyroid levels and managing and treating hypothyroidism on an optimal medication dosage, all from the comfort of your home. Learn more about the benefits of a Paloma membership today, and get on your way to better thyroid health!


American Thyroid Association. Hypothyroidism. American Thyroid Association. Published 2023. Accessed April 10, 2024.

Jonklaas J, Bianco AC, Bauer AJ, Burman KD, Cappola AR, Celi FS, Cooper DS, Kim BW, Peeters RP, Rosenthal MS, Sawka AM; American Thyroid Association Task Force on Thyroid Hormone Replacement. Guidelines for the treatment of hypothyroidism: prepared by the american thyroid association task force on thyroid hormone replacement. Thyroid. 2014 Dec;24(12):1670-751. doi:

Wiesner A, Gajewska D, Paśko P. Levothyroxine Interactions with Food and Dietary Supplements-A Systematic Review. Pharmaceuticals (Basel). 2021 Mar 2;14(3):206. doi:

Synthroid (levothyroxine) package insert. North Chicago, IL; AbbVie, Inc. Feb 2024.

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Emilie White, PharmD

Clinical Pharmacist and Medical Blogger

Emilie White, PharmD is a clinical pharmacist with over a decade of providing direct patient care to those hospitalized. She received her Doctor of Pharmacy degree from Massachusetts College of Pharmacy and Health Sciences. After graduation, Emilie completed a postgraduate pharmacy residency at Bon Secours Memorial Regional Medical Center in Virginia. Her background includes caring for critical care, internal medicine, and surgical patients.

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