Drug & supplement interaction

Lactobacillus Johnsonii + 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 Lactobacillus Johnsonii 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

Lactobacillus Johnsonii 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 Lactobacillus Johnsonii 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.

Lactobacillus Johnsonii safety at a glance

Lactobacillus John... overall Use caution Generally well tolerated in healthy adults, but people who are seriously ill or immune-compromised should be cautious.
Pregnancy Use caution There is not enough reliable safety data, so use only with a doctor's guidance.
Breastfeeding Use caution Safety has not been well studied, so check with a healthcare provider before using.

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

Still wondering about combining Levothyroxine and Lactobacillus Johnsonii? 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. Lactobacillus Johnsonii has documented interactions with 1 drug class — the most serious being antibiotic 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

Lactobacillus Johnsonii Does Interact With Other Medications

Lactobacillus Johnsonii has 182 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 182 No known interaction 2,648 (incl. Levothyroxine)
Taking anything else?

Check Another of Your Medications Against Lactobacillus Johnsonii

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

What to actually watch for

What Lactobacillus Johnsonii Itself Has Been Linked To

This is not an interaction — nothing below involves Levothyroxine. It is the side-effect record for Lactobacillus Johnsonii on its own, from the licensed Natural Medicines monograph. If something new turns up after you add Lactobacillus Johnsonii, this list is the first place to look. One entry is worth acting on rather than waiting out — marked below.

  • A higher chance of infection Worth acting on Additional detail

    “Since Lactobacillus johnsonii preparations contain live and active microorganisms, there is some concern that they might cause pathogenic infection in some patients. Some lactobacilli species have been isolated in cases of bacteremia, sepsis, splenic abscess, endocarditis, necrotizing fasciitis, pancreatic necrosis, and meningoencephalitis.”

    Lactobacillus Johnsonii · Natural Medicines adverse-effect record, reported in sepsis.

    1 source cited
    1. 107543. Rossi F, Amadoro C, Gasperi M, Colavita G. Lactobacilli infection case reports in the last three years and safety implications. Nutrients. 2022;14(6):1178. PubMed

Everything above comes from the Natural Medicines adverse-effect record for Lactobacillus Johnsonii — expand a row for the licensed statement it rests on. We read the ADVERSE REACTIONS section of Levothyroxine’s FDA label too, and the two lists don’t meaningfully overlap — which is why no Levothyroxine column appears here.

How to take them

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

At least one FDA label for a product containing Levothyroxine says to take it on an empty stomach. Most supplements — Lactobacillus Johnsonii 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 Lactobacillus Johnsonii 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.

Overlapping uses

What Levothyroxine Is Prescribed For, and What Lactobacillus Johnsonii Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Levothyroxine is a prescription medicine with approved uses on its FDA label. Lactobacillus Johnsonii is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Levothyroxine is prescribed for: 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.

Lactobacillus Johnsonii has been studied for:

  • Constipation studied, not established Lactobacillus Johnsonii has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

    Lactobacillus Johnsonii for constipation

    It is unclear if oral Lactobacillus johnsonii is beneficial in patients with constipation.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Levothyroxine on your own; if you are taking Lactobacillus Johnsonii for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Lactobacillus Johnsonii 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 Lactobacillus Johnsonii 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 Lactobacillus Johnsonii 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 Lactobacillus Johnsonii as Part of a Dietary Supplement Product? Check It for Interactions

We hold 17 real supplement products containing Lactobacillus Johnsonii, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Lactobacillus Johnsonii. Even though Lactobacillus Johnsonii 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 Lactobacillus Johnsonii 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 Lactobacillus Johnsonii
Steady interest

#1,365 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 Lactobacillus Johnsonii reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Lactobacillus Johnsonii and Levothyroxine records this page draws on were last updated July 10, 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 Lactobacillus Johnsonii

What is Lactobacillus Johnsonii?

  • Digestive and gut health
  • Supporting healthy gut bacteria
  • Diarrhea prevention or relief
  • Immune support
  • Helping with stomach (H. pylori) discomfort

Lactobacillus johnsonii is a probiotic bacterium found naturally in the human gut and in some fermented foods, and it is used mainly for digestive and immune support. Human evidence for most specific health claims is still limited, so its benefits are uncertain. It is generally well tolerated in healthy people, but anyone with a weakened immune system, serious illness, or who is pregnant should talk to a pharmacist or doctor first.

Lactobacillus johnsonii · Lactobacillaceae · Whole live bacteria (probiotic culture) · Capsules, tablets, powders, and fermented foods or dairy products containing the live culture

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

Lactobacillus Johnsonii: dosing

There is no official standardized dose for Lactobacillus johnsonii. Probiotic amounts are usually measured in colony-forming units (CFUs), and products vary widely.The best approach is to follow the directions on the product label and not exceed the recommended amount.

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

Read the full Lactobacillus Johnsonii 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 & Lactobacillus Johnsonii

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

0Major
182Moderate
0Minor
2,647No known interaction
182 Moderate 2,647 No interaction
Moderate

182 interactions

Showing 60 of 182 moderate interactions — see all 182 on the Lactobacillus Johnsonii page.

No interaction 2,647 drugs checked — show the list

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

Showing the 60 most looked-up of 2,647 medications checked with no known interaction — see the full Lactobacillus Johnsonii list.

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

Lactobacillus Johnsonii References

The 2 references that drive our Lactobacillus Johnsonii 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. Pierce A. The American Pharmaceutical Association Practical Guide to Natural Medicines. New York: The Stonesong Press, 1999:19.
  2. Rossi F, Amadoro C, Gasperi M, Colavita G. Lactobacilli infection case reports in the last three years and safety implications. Nutrients. 2022;14(6):1178. 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 Lactobacillus Johnsonii and Levothyroxine Together: Common Questions

Is it safe to take Lactobacillus Johnsonii with Levothyroxine?
We do not list a known interaction between Lactobacillus Johnsonii 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 Lactobacillus Johnsonii 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 Lactobacillus Johnsonii 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.
Are Lactobacillus Johnsonii and Levothyroxine used for the same thing?
They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for Lactobacillus Johnsonii in each. That is a conversation for your prescriber, especially if Levothyroxine is being adjusted to a target.
How was the Lactobacillus Johnsonii and Levothyroxine combination checked?
Interactions in our licensed database are recorded against drug classes. Levothyroxine is filed under 3 classifications, and Lactobacillus Johnsonii has documented interactions with 1 drug class — 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 Lactobacillus Johnsonii interact with any other medications?
Yes. Lactobacillus Johnsonii has 182 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 — Lactobacillus Johnsonii 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

Lactobacillus Johnsonii 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 2 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Levothyroxine and Lactobacillus Johnsonii?

Our pharmacists answer your medication & supplement questions — free.

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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.