Drug & supplement interaction

Rehmannia + Levothyroxine

Levothyroxine brand names: Euthyrox, Levothroid, Unithroid, Synthroid, Levoxyl, and others.

No Known Interaction
Medically reviewed by · Updated June 2026 · Pair last verified Sep 13, 2026
The bottom line No known interaction

We found no known interaction between Rehmannia and Levothyroxine in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the label for Levothyroxine states a food rule worth keeping to.

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Interaction report

Rehmannia and Levothyroxine

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Levothyroxine and Rehmannia in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Rehmannia safety at a glance

Rehmannia overall Use caution Generally used in traditional medicine, but human safety data are limited and quality varies between products.
Pregnancy Avoid Not enough safety information; best avoided during pregnancy.
Breastfeeding Avoid Not enough safety information; best avoided while breastfeeding.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Levothyroxine and Rehmannia? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Levothyroxine

Interactions in our licensed database are recorded against drug classes, not just single drug names. Levothyroxine is filed under 3 classifications — including thyroid hormone, oral drugs. Rehmannia has documented interactions with 2 drug classes — the most serious being antidiabetes drugs (moderate) and antihypertensive drugs (moderate) — and none of Levothyroxine’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Rehmannia Does Interact With Other Medications

Rehmannia has 258 moderate known drug interactions in our database — Levothyroxine isn’t one of them. If you take anything else, check it against the full list below.

Moderate 258 No known interaction 2,572 (incl. Levothyroxine)
Taking anything else?

Check Another of Your Medications Against Rehmannia

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

What to actually watch for

What Levothyroxine’s Own FDA Label Lists

This is not an interaction — none of it involves Rehmannia. These are the most notable effects listed in the ADVERSE REACTIONS section of Levothyroxine’s own FDA label, for the medication by itself. Knowing the drug’s own list makes it easier to work out the likely cause if something new turns up while you take both. 10 of them are worth acting on rather than waiting out — marked below.

  • A change in thyroid levels Worth acting on
  • Bone thinning Worth acting on
  • Muscle weakness Worth acting on
  • A heart attack Worth acting on
  • Heart failure Worth acting on
  • Wheezing Worth acting on
  • Seizures Worth acting on
  • Chest pain Worth acting on
  • Shortness of breath Worth acting on
  • A severe allergic reaction Worth acting on

Showing the 10 most notable of 32 label-listed effects — ranked by how unusual each one is across medicines generally, with serious effects weighted up.

From the ADVERSE REACTIONS section of the FDA label for Levothyroxine. Read the label on DailyMed › Rehmannia’s licensed record lists no adverse effects our clinical vocabulary could match, so there is no Rehmannia side to compare — that is a limit of the record, not a statement that Rehmannia has no side effects.

How to take them

Some Levothyroxine Products Have a Food Rule — Rehmannia Should Not Break It

At least one FDA label for a product containing Levothyroxine says to take it on an empty stomach. Most supplements — Rehmannia included — are taken with a meal, so the easy mistake is swallowing both together at breakfast. Where that rule applies, keep Levothyroxine on its own and move Rehmannia to a meal later in the day.

This may not be true of your version. Food instructions belong to the product, not the ingredient: two Levothyroxine products can carry different directions, and extended-release forms often differ from immediate-release ones. The label we read is quoted below — check the directions on your own box or bottle, or ask your pharmacist, for how to take the exact product you were given.

A food rule is not an interaction — it is about how much of the medicine you absorb. The directions that came with your own product, and your pharmacist, outrank anything on this page.

From our Q&A

Questions About Rehmannia or Levothyroxine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Rehmannia or Levothyroxine, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Levothyroxine

This page covers Rehmannia only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Levothyroxine 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).

By severity: 2 major · 39 moderate · 9 minor.

From our pharmacist’s overview on the Levothyroxine page

“Levothyroxine replaces a hormone your body measures in tiny amounts, so small shifts in its blood level show up in how you feel, and I treat this list with genuine care. Nearly everything on it does one of two things: blocks the pill from being absorbed in the gut, the way everyday minerals like calcium do by binding it into complexes,…”

Reviewed by 2 · Jul 18, 2026

Open the Levothyroxine interaction page

One more smart check

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

We hold 861 real supplement products containing Rehmannia, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Rehmannia. Even though Rehmannia itself has no known interaction with Levothyroxine, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Rehmannia and Levothyroxine 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 Rehmannia
Top 25%

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

29 days ago today
Medication Levothyroxine
Top 10

#2 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.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Rehmannia reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Rehmannia and Levothyroxine records this page draws on were last updated June 22, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Rehmannia

What is Rehmannia?

  • Kidney and adrenal support
  • Anemia and blood building (traditional)
  • Inflammatory conditions
  • Allergies
  • Fatigue and aging-related complaints

Rehmannia is a root used for centuries in Traditional Chinese Medicine, often to 'tonify' the kidneys and support energy or blood health. Human evidence for most modern uses is limited, so it should be viewed as unproven rather than reliable. Talk with a pharmacist or doctor before trying it, especially if you are pregnant, breastfeeding, or take other medicines.

Rehmannia glutinosa · Orobanchaceae · Root (raw or steam-prepared) · Dried root, decoctions/teas, capsules, tinctures, and ingredient in multi-herb formulas

An interaction check asks whether these two react with each other — it does not ask whether Rehmannia is a good idea for someone in your situation. Here is what our Rehmannia record says about it on its own.

Rehmannia: dosing

There is no official, well-established standardized dose for Rehmannia. Traditional use varies widely depending on the form (raw versus prepared root), whether it is a tea, capsule, or tincture, and whether it is part of a larger herbal formula.The safest approach is to follow the directions on the product label and not exceed them.

From our Rehmannia monograph — the full record covers uses, side effects and every documented interaction.

Read the full Rehmannia monograph & all interactions
Medication

About Levothyroxine

What Is Levothyroxine Used For?

Brand names: Euthyrox, Levothroid, Unithroid, Synthroid, Levoxyl, Levo-T, Eltroxin, Estre, Levothyroxine, Novothyrox, Levolet

Levothyroxine replaces or supplements the thyroid hormone your body isn't making enough of. It's used for hypothyroidism — an underactive thyroid — in adults, children, and even newborns, whether the cause is the thyroid gland itself, the pituitary gland, or the hypothalamus in the brain.

It's also used alongside surgery and radioiodine treatment in people with certain types of thyroid cancer, to help suppress the hormone that can stimulate cancer growth. It is not meant for weight loss, treating benign thyroid nodules in people who have enough iodine, or for hypothyroidism during recovery from a temporary condition called subacute thyroiditis.

See full Levothyroxine drug information
Keep checking

Other Drugs & Rehmannia

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

0Major
258Moderate
0Minor
2,571No known interaction
258 Moderate 2,571 No interaction
Moderate

258 interactions

Showing 60 of 258 moderate interactions — see all 258 on the Rehmannia page.

No interaction 2,571 drugs checked — show the list

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

Showing the 60 most looked-up of 2,571 medications checked with no known interaction — see the full Rehmannia list.

See the full Rehmannia interactions page
See every supplement checked against Levothyroxine, ranked by severity
Evidence & sources

Rehmannia References

The 3 references that drive our Rehmannia monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Zhang R, Zhou J, Jia Z, et al. Hypoglycemic effect of Rehmannia glutinosa oligosaccharide in hyperglycemic and alloxan-induced diabetic rats and its mechanism. J Ethnopharmacol 2004;90:39-43. PubMed
  2. Zhang RX, Li MX, Jia ZP. Rehmannia glutinosa: review of botany, chemistry and pharmacology. J Ethnopharmacol 2008;117(2):199-214. PubMed
  3. Chao CH, Hsu JL, Chen MF, et al. Anti-hypertensive effects of Radix Rehmanniae and its active ingredients. Nat Prod Res. 2020;34(11):1547-1552.

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Rehmannia and Levothyroxine Together: Common Questions

Is it safe to take Rehmannia with Levothyroxine?
We do not list a known interaction between Rehmannia and Levothyroxine. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Should I take Rehmannia and Levothyroxine at the same time of day?
At least one FDA label for a product containing Levothyroxine says to take it on an empty stomach, and supplements are usually taken with a meal — so taking them together at breakfast is the easy mistake. Where that applies, keep Levothyroxine on its own and move Rehmannia to a meal later in the day. Food instructions belong to the product rather than the ingredient, so check the directions on your own box. This is about absorption, not an interaction.
How was the Rehmannia and Levothyroxine combination checked?
Interactions in our licensed database are recorded against drug classes. Levothyroxine is filed under 3 classifications, and Rehmannia has documented interactions with 2 drug classes — none of Levothyroxine's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Rehmannia interact with any other medications?
Yes. Rehmannia has 258 documented drug interactions in our database — Levothyroxine is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Levothyroxine interact with any supplements?
Yes. Levothyroxine has documented interactions with 50 supplements in our database — Rehmannia is not one of them. The Levothyroxine interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Rehmannia monograph Uses, safety profile, and every drug interaction in one place Levothyroxine drug information The full plain-English guide to this medication Levothyroxine supplement interactions Every supplement checked against Levothyroxine, 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 References The 3 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Levothyroxine and Rehmannia?

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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.