Best Supplements to Take with Levothyroxine (and Which Ones to Avoid)

Jul 9, 2026

Best Supplements to Take with Levothyroxine (and Which Ones to Avoid)

Quick Answer

Yes, you can usually take supplements while taking levothyroxine—but timing matters.

Unlike many medicines, the biggest consideration with levothyroxine isn't whether you can take supplements, but when you take them. Certain supplements, particularly calcium, iron and magnesium, can reduce the absorption of levothyroxine if taken too close together.

That doesn't mean you should avoid these supplements altogether. Many people taking levothyroxine can benefit from them if they're appropriate for their individual needs. The key is leaving enough time between your medication and your supplements.

In this guide, we'll explain:

Which supplements may be worth considering.
Which supplements should be avoided or separated from levothyroxine.
How to choose high-quality supplements.
When it's worth speaking to your GP or pharmacist.

Pharmacist's Verdict

Question	Answer
Can I take supplements with levothyroxine?	✅ Yes, in most cases.
Is timing important?	✅ Yes — some supplements can reduce levothyroxine absorption if taken together.
Which supplements need the most attention?	✅ Calcium, iron and magnesium.
Are there supplements to avoid?	✅ Some should be taken at a different time of day rather than avoided completely.

Where Should You Start?

If you're taking levothyroxine, the first thing to think about is timing.

Some supplements can bind to levothyroxine in the gut and reduce how much of the medicine your body absorbs. This is why calcium, iron and magnesium usually need to be taken several hours away from your levothyroxine dose.

Supplement	When to consider it	Key point
High-quality multivitamin	If you're looking for general nutritional support	Check whether it contains calcium, iron or magnesium and take it away from levothyroxine.
Vitamin D	If you have low sun exposure or are at risk of deficiency	Usually fine with levothyroxine, but follow your supplement instructions.
Calcium	If you have low intake or need bone health support	Take several hours away from levothyroxine.
Iron	If you have confirmed or suspected iron deficiency	Take several hours away from levothyroxine.
Magnesium	If your dietary intake is low or you want magnesium support	Take several hours away from levothyroxine.

The aim isn't to avoid useful supplements. It's to take them at the right time so they don't interfere with your thyroid medication.

Supplements That May Be Worth Considering

A High-Quality Multivitamin

A well-formulated multivitamin can be useful if you're looking for general nutritional support. The important thing is to check whether it contains minerals such as calcium, iron or magnesium, as these should be taken several hours away from levothyroxine.

(TRINITY is pharmacist formulated, uses bioavailable nutrient forms and separates nutrients across Morning, Day and Night formulations.)

Vitamin D

Vitamin D is commonly considered by people with thyroid conditions, especially if they have limited sun exposure or have previously been advised their levels are low. Vitamin D contributes to normal immune function, normal muscle function and the maintenance of normal bones.

Calcium

Calcium may be appropriate if your dietary intake is low or you've been advised to support your bone health. However, calcium can reduce levothyroxine absorption if taken too close together, so timing is essential.

Iron

Iron should generally only be supplemented if deficiency is suspected or confirmed. Like calcium, iron can reduce levothyroxine absorption if taken at the same time.

Magnesium

Magnesium may be useful for people with low dietary intake or those looking for muscle and nervous system support. It should also be taken several hours away from levothyroxine.

(Magnesium Complex contains magnesium bisglycinate and magnesium taurate with no magnesium oxide.)

Supplements to Avoid (or Use with Caution)

With levothyroxine, most supplements don't need to be avoided completely. The main issue is taking certain supplements too close to your medication.

Supplement	Recommendation	Why?
Calcium	⚠️ Separate from levothyroxine	Calcium can reduce levothyroxine absorption if taken at the same time.
Iron	⚠️ Separate from levothyroxine	Iron can bind to levothyroxine and reduce how much your body absorbs.
Magnesium	⚠️ Separate from levothyroxine	Magnesium may interfere with levothyroxine absorption if taken too close together.
Multivitamins containing minerals	⚠️ Check timing	Many multivitamins contain calcium, iron or magnesium, so they should usually be taken several hours apart from levothyroxine.
Kelp or iodine supplements	⚠️ Use with caution	Extra iodine isn't suitable for everyone with thyroid conditions and should be discussed with your GP or pharmacist.

The key point is simple: take levothyroxine on its own, then take mineral-containing supplements later in the day unless your healthcare professional has advised otherwise.

When Is It Worth Seeking Advice?

If you're taking levothyroxine, speak to your GP or pharmacist before starting supplements if:

You've recently started levothyroxine or your dose has changed.
You're planning to take calcium, iron or magnesium supplements.
Your thyroid symptoms aren't improving despite taking your medication.
You're taking several prescription medicines or supplements.
You're pregnant, breastfeeding or planning a pregnancy.
You have another thyroid condition or a long-term medical condition.

Your healthcare professional can advise you on the best timing for both your medication and any supplements. In many cases, the issue isn't what you're taking—it's when you take it.

Frequently Asked Questions

Can I take supplements with levothyroxine?

Yes. Most supplements can be taken safely with levothyroxine, but some need to be taken at a different time of day to avoid reducing how well your medication is absorbed.

What are the best supplements to take with levothyroxine?

A high-quality multivitamin, vitamin D or magnesium may be appropriate depending on your individual needs. If you're considering calcium or iron, make sure they're taken several hours away from your levothyroxine.

Can I take a multivitamin with levothyroxine?

Yes, but check whether it contains calcium, iron or magnesium. If it does, it should usually be taken several hours after your levothyroxine rather than at the same time.

Can I take magnesium with levothyroxine?

Yes. Magnesium can generally be taken safely with levothyroxine, but it should be taken several hours apart to avoid affecting absorption.

Can I take calcium with levothyroxine?

Yes, but not at the same time. Calcium supplements can reduce levothyroxine absorption, so they should be separated by several hours.

Can I take iron with levothyroxine?

Yes. Iron supplements are safe for most people when clinically appropriate, but they should also be taken several hours away from your levothyroxine dose.

Can I take vitamin D with levothyroxine?

Yes. Vitamin D doesn't interfere with levothyroxine absorption and can generally be taken safely alongside it.

Can I take iodine supplements with levothyroxine?

Not routinely. Unless you've been advised by your GP or specialist, iodine supplements aren't recommended for most people taking levothyroxine.

Should I stop taking levothyroxine if I'm worried about supplement interactions?

No. Continue taking levothyroxine as prescribed. In most cases, interactions can be avoided simply by taking supplements at a different time of day rather than stopping your medication.

References

British National Formulary (BNF). Levothyroxine.
National Institute for Health and Care Excellence (NICE). Thyroid disease: assessment and management.
NHS. Levothyroxine.
British Thyroid Foundation. Levothyroxine: Taking Your Medication.
European Food Safety Authority (EFSA). Authorised Health Claims for Vitamins and Minerals.
Joint Formulary Committee. British National Formulary (BNF Online).