Is It Safe To Take Probiotics With Synthroid?

In our latest question and answer, the pharmacist discusses taking probiotics with the thyroid replacement medication Synthroid.

Question

I am currently on Synthroid, which I take first thing in the morning. I have also started taking Phillips Colon Health probiotics for constipation. Can I take the probiotics an hour after the Synthroid when I eat breakfast, or will that impair the absorption of the Synthroid (as I know many supplements do)? Thanks.

Asked by Mike On Sep 16, 2022

Answered by
Medical Content Reviewed By HelloPharmacist Staff

Published Sep 16, 2022
Last updated Apr 18, 2024

Key points

  • There is no known interaction between Synthroid and probiotic supplements.
  • Probiotics should be taken at least 30 to 60 minutes after taking Synthroid to avoid interference with absorption.

Answer

Probiotic supplements should be safe to take the same day as Synthroid (levothyroxine). However, they should be taken at least 30 to 60 minutes after taking Synthroid to avoid negatively affecting the absorption of the drug.

The prescribing information for Synthroid, as well as most studies, recommend taking the drug by itself at least 30 to 60 minutes before food or other medications to allow it to absorb consistently.

Taking it with other drugs or food can decrease absorption, potentially making the medication less effective, which could lead to symptoms of hypothyroidism (e.g. lethargy, weight gain, feeling of cold, etc...).

It is even recommended to separate some drugs by more than 60 minutes. These include:

  • Fiber supplements
  • Antacids
  • Calcium supplements
  • Magnesium supplements

All of the above are recommended to be separated from Synthroid by at least four hours.

There have been no studies evaluating how probiotics could potentially affect Synthroid absorption if taken at the same time.

However, one study was completed where a probiotic supplement (VSL#3) was taken at least 2 hours after Synthroid. The study showed that, when compared to individuals that did not take the probiotic, there was no difference in thyroid-stimulating hormone (TSH), fT3 (free triiodothyronine), and fT4 (free tetraiodothyronine) levels.

So, as long as you separate your probiotic supplement from Synthroid by the appropriate amount of time (at least 30 to 60 minutes), you should be safe (although it should be noted that some studies suggest that our intestinal bacteria flora can affect thyroid hormone levels in general).

Final Words

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References

  • Synthroid Prescribing Information, Abbvie
  • Clinical relevancy of the levothyroxine-continuous enteral nutrition interaction, PubMed
  • Conditions and drugs interfering with thyroxine absorption, PubMed
  • Probiotics Ingestion Does Not Directly Affect Thyroid Hormonal Parameters in Hypothyroid Patients on Levothyroxine Treatment, PubMed
  • Link between hypothyroidism and small intestinal bacterial overgrowth, PubMed

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Dr. Brian has been practicing pharmacy for over 13 years and has wide-ranging experiences in many different areas of the profession. From retail, clinical, program development, and administrative responsibilities, he's your knowledgeable and go-to source for all your pharmacy and medication-related questions! Dr. Brian Staiger also has herbalist training and educational certificates in the field of medical ethnobotany. Feel free to send him an email at [email protected]! You can also connect with Dr. Brian Staiger on LinkedIn.

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