Drug & supplement interaction

Khella + Levothyroxine

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

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

We found no known interaction between Khella 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, and the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Khella 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 Khella 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.

Khella safety at a glance

Khella overall Use caution May cause side effects like nausea and sun sensitivity, and quality of evidence is limited.
Pregnancy Likely Unsafe When used orally. The active constituent, khellin, has uterine stimulant activity; contraindicated. Read the full pregnancy detail
Breastfeeding Avoid Not enough safety data; avoid use while breastfeeding.

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Levothyroxine and Khella? 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. Khella has documented interactions with 3 drug classes — the most serious being digoxin (lanoxin) (moderate), hepatotoxic drugs (moderate) and photosensitizing 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

Khella Does Interact With Other Medications

Khella has 618 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 618 No known interaction 2,212 (incl. Levothyroxine)
Taking anything else?

Check Another of Your Medications Against Khella

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

What to actually watch for

No Interaction Found — But Data Suggests Khella and Levothyroxine May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Trouble sleeping / Headache Additional detail

    Khella

    “Orally, prolonged use or use of high doses of khella can cause nausea, dizziness, constipation, lack of appetite, headache, itching, and insomnia. In some patients, khella can cause elevated liver transaminase and gamma-glutamyltransferase (GGT) levels (2). There is also some concern that khella might cause photosensitivity (2,7162).”

    Khella · Natural Medicines adverse-effect record, reported in cluster headache.

    2 sources cited
    1. 2. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.
    2. 7162. Dr. Duke's Phytochemical and Ethnobotanical Databases. Available at: http://www.ars-grin.gov/duke/.

    “Orally, prolonged use or use of high doses of khella can cause dizziness, headache, and insomnia (2).”

    Khella · Natural Medicines adverse-effect record, reported in cluster headache.

    1 source cited
    1. 2. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.

    Levothyroxine

    Listed in the ADVERSE REACTIONS section of the FDA label for Levothyroxine. Read the label on DailyMed ›

  • Itching Additional detail

    Khella

    “Orally, prolonged use or use of high doses of khella can cause itching (2). There is also some concern that khella might cause photosensitivity because of the constituents khellin and furocoumarin (2,7162).”

    Khella · Natural Medicines adverse-effect record, reported in pruritus.

    2 sources cited
    1. 2. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.
    2. 7162. Dr. Duke's Phytochemical and Ethnobotanical Databases. Available at: http://www.ars-grin.gov/duke/.

    Levothyroxine

    Listed in the ADVERSE REACTIONS section of the FDA label for Levothyroxine. Read the label on DailyMed ›

  • Nausea Additional detail

    Khella

    “Orally, prolonged use or use of high doses of khella can cause nausea, constipation, and lack of appetite (2).”

    Khella · Natural Medicines adverse-effect record, reported in constipation.

    1 source cited
    1. 2. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.

    Levothyroxine

    Listed in the ADVERSE REACTIONS section of the FDA label for Levothyroxine. Read the label on DailyMed ›

Reported for Khella but not commonly for Levothyroxine: reduced appetite, sun sensitivity, constipation and dizziness.

Effects for Levothyroxine come from the ADVERSE REACTIONS section of its FDA label; effects for Khella come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Khella in Pregnancy & Breastfeeding

Pregnancy Likely Unsafe

When used orally. The active constituent, khellin, has uterine stimulant activity; contraindicated.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

How to take them

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

At least one FDA label for a product containing Levothyroxine says to take it on an empty stomach. Most supplements — Khella 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 Khella 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 Khella 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 Khella 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 Khella 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 Khella as Part of a Dietary Supplement Product? Check It for Interactions

We hold 43 real supplement products containing Khella, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Khella. Even though Khella 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 Khella 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 Khella
Steady interest

#1,230 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 Khella reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Khella and Levothyroxine records this page draws on were last updated July 11, 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 Khella

What is Khella?

Khella
  • Asthma and bronchitis
  • Angina and heart-related chest pain
  • Kidney stones
  • Vitiligo and psoriasis
  • Mild high blood pressure

Khella is a Mediterranean herb whose seeds contain compounds like khellin that may relax smooth muscle in the airways and blood vessels. While it has a long history of traditional use for breathing and heart problems, modern evidence in supplement form is limited, and it can cause side effects and sun sensitivity, so talk with your pharmacist or doctor before using it.

Ammi visnaga · Apiaceae · Dried ripe fruit (seeds) · Capsules, tinctures, teas, standardized extracts

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

Khella: dosing

There is no well-established, standardized dose for khella supplements. The right amount depends on the product, how it is prepared, and the amount of active compounds it contains.Because strength varies widely between products, follow the directions on the label and do not exceed them. Avoid long-term use unless guided by a healthcare professional.

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

Read the full Khella 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 & Khella

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

0Major
618Moderate
0Minor
2,211No known interaction
618 Moderate 2,211 No interaction
Moderate

618 interactions

Showing 60 of 618 moderate interactions — see all 618 on the Khella page.

No interaction 2,211 drugs checked — show the list

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

Showing the 60 most looked-up of 2,211 medications checked with no known interaction — see the full Khella list.

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

Khella References

The 10 references that drive our Khella 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. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.
  2. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  3. Abdel-Fattah A, Aboul-Enein MN, Wassel GM, El-Menshawi BS. An approach to the treatment of vitiligo by khellin. Dermatologica 1982;165:136-40. PubMed
  4. Duarte J, Torres AI, Zarzuelo A. Cardiovascular effects of visnagin on rats. Planta Med 2000;66:35-9. PubMed
  5. Abdel-Fattah A, Aboul-Enein MN, Wassel G, El-Menshawi B. Preliminary report on the therapeutic effect of khellin in psoriasis. Dermatologica 1983;167:109-10. PubMed
  6. Ossenkoppele PM, van der Sluis WG, van Vloten WA. [Phototoxic dermatitis following the use of Ammi majus fruit for vitiligo]. Ned Tijdschr Geneeskd 1991;135:478-80.
  7. Harvengt C, Desager JP. HDL-cholesterol increase in normolipaemic subjects on khellin: a pilot study. Int J Clin Pharmacol Res 1983;3:363-6.
  8. Dr. Duke's Phytochemical and Ethnobotanical Databases. Available at: http://www.ars-grin.gov/duke/.
  9. de Leeuw J, van der BN, Maierhofer G, et al. A case study to evaluate the treatment of vitiligo with khellin encapsulated in L-phenylalanin stabilized phosphatidylcholine liposomes in combination with ultraviolet light therapy. Eur J Dermatol 2003;13(5):
  10. Orecchia G, Perfetti L. Photochemotherapy with topical khellin and sunlight in vitiligo. Dermatology 1992;184(2):120-123. PubMed

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 Khella and Levothyroxine Together: Common Questions

Is it safe to take Khella with Levothyroxine?
We do not list a known interaction between Khella 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.
Do Khella and Levothyroxine have any of the same side effects?
Yes — our sources link each of them separately to 4 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
Should I take Khella 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 Khella 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 Khella and Levothyroxine combination checked?
Interactions in our licensed database are recorded against drug classes. Levothyroxine is filed under 3 classifications, and Khella has documented interactions with 3 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 Khella interact with any other medications?
Yes. Khella has 618 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 — Khella 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

Khella 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 10 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Levothyroxine and Khella?

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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.