Drug & supplement interaction

Celery + Levothyroxine Sodium

Levothyroxine Sodium brand names: Tirosint-Sol, Thyquidity, Ermez.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Celery has a moderate interaction with Levothyroxine Sodium. Theoretically, celery seed might decrease the effects of levothyroxine.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Celery and Levothyroxine Sodium

Here is the interaction we found between these two, with the evidence behind it.

Moderate

LEVOTHYROXINE (Synthroid, others)

Theoretically, celery seed might decrease the effects of levothyroxine.
Several cases of hypothyroidism with low T4 levels have been reported in people who were previously stabilized on levothyroxine and then started taking celery seed tablets. They presented with symptoms such as lethargy, bloating, and dry skin, and recovered when celery seed was stopped. However, celery stem and leaf has been associated with case reports of hyperthyroidism in patients with no pre-existing thyroid disorders.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the practical takeaway if you take levothyroxine for an underactive thyroid. There are a handful of real-world reports where folks who were doing well on their thyroid pill started taking celery seed tablets and then slid back into low thyroid symptoms, things like feeling sluggish, bloated, dry skin, and just dragging through the day. Their T4 levels dropped, and when they stopped the celery seed, they bounced back. So the concern is that concentrated celery seed could weaken how well your levothyroxine works.

To be honest, this is based on a few anecdotes, not strong studies, so I wouldn't lose sleep over it. Eating celery as a normal vegetable is very unlikely to matter. Concentrated supplement doses are the question mark. Please don't stop either one on your own. Just give your pharmacist or doctor a heads-up so they can check your thyroid levels if needed.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Moses, G. Thyroxine interacts with celery seed tablets? Australian Prescriber 2001;24:6-7. DOI
  2. Maljaei MB, Moosavian SP, Mirmosayyeb O, Rouhani MH, Namjoo I, Bahreini A. Effect of celery extract on thyroid function; is herbal therapy safe in obesity? Int J Prev Med 2019;10:55. doi: 10.4103/ijpvm.IJPVM_209_17. PubMed
  3. Rouhi-Boroujeni H, Hosseini M, Gharipour M, Rouhi-Boroujeni H. Is herbal therapy safe in obesity? A case of Apium graveolens (Celery) induced hyperthyroidism. ARYA Atheroscler 2016;12(5):248-9.

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Celery Also Interacts With Other Medications

Celery has 448 moderate, 202 minor known drug interactions in our database — the Levothyroxine Sodium one above is one of them. If you take anything else, check it against the full list below.

Moderate 448 Minor 202 No known interaction 2,180 (incl. Levothyroxine Sodium)
Taking anything else?

Check Another of Your Medications Against Celery

Covers the 2,830 medications we’ve checked against Celery. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Levothyroxine Sodium

This page covers Celery only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Levothyroxine Sodium page lists 50 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Tiratricol (major), Acetyl-l-carnitine (moderate), Alpha-lipoic Acid (moderate) and Ascophyllum Nodosum (moderate).

Open the Levothyroxine Sodium interaction page

One more smart check

Taking Celery as Part of a Dietary Supplement Product? Check It for Interactions

We hold 1,687 real supplement products containing Celery, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Celery. Your product may carry other ingredients that interact with Levothyroxine Sodium too, on top of Celery — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Celery and Levothyroxine Sodium Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Celery
Top 25%

#168 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Levothyroxine Sodium
Top 5%

#126 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Celery

What is Celery?

Celery
  • High blood pressure
  • Fluid retention (diuretic)
  • Joint pain and inflammation
  • Anxiety and sleep
  • Digestive support

Celery is a common vegetable that is also taken as a seed extract or oil supplement, mainly for blood pressure, fluid retention, and joint discomfort. Human evidence for these supplement uses is limited and mostly preliminary, so it should not replace proven treatments. Celery is generally safe as food, but concentrated supplements and possible allergic reactions warrant caution.

Read the full Celery monograph & all interactions
Keep checking

Other Drugs & Celery

Browse every other medication we’ve checked against Celery — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
448Moderate
202Minor
2,179No known interaction
448 Moderate 202 Minor 2,179 No interaction
Moderate

448 interactions

Showing 60 of 448 moderate interactions — see all 448 on the Celery page.

Minor

202 interactions

Showing 60 of 202 minor interactions — see all 202 on the Celery page.

No interaction 2,179 drugs checked — show the list

We also checked Celery against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,179 medications checked with no known interaction — see the full Celery list.

See the full Celery interactions page
See every supplement checked against Levothyroxine Sodium, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Celery monograph › Uses, safety, and every drug interaction in one place Levothyroxine Sodium supplement interactions › Every supplement checked against Levothyroxine Sodium, ranked by severity Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Celery and Levothyroxine Sodium Together: Common Questions

Can you take Celery with Levothyroxine Sodium?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Celery and Levothyroxine Sodium interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Levothyroxine Sodium and Celery?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.