Drug & supplement interaction

Nadh + 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 Nadh 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

Nadh 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 Nadh 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.

Worth understanding: our licensed dataset holds no drug-interaction record for Nadh at all — not against Levothyroxine, and not against any other medication we track. This verdict therefore rests on the absence of any recorded data, not on research that looked at this combination and found nothing. We cannot rule an interaction out.

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.

Nadh safety at a glance

Nadh overall Use caution Generally well tolerated short-term, but long-term safety and quality data are limited.
Pregnancy Avoid Not enough safety information; best to avoid during pregnancy.
Breastfeeding Avoid Not enough safety information; best to avoid while breastfeeding.

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

Still wondering about combining Levothyroxine and Nadh? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
What to actually watch for

What Levothyroxine’s Own FDA Label Lists

This is not an interaction — none of it involves Nadh. 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 › Nadh’s licensed record lists no adverse effects our clinical vocabulary could match, so there is no Nadh side to compare — that is a limit of the record, not a statement that Nadh has no side effects.

How to take them

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

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

Nadh has been studied for:

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

    Nadh for depression

    Although there has been interest in using oral and parenteral NADH for depression, there is insufficient reliable information about the clinical effects of NADH for this purpose.

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 Nadh for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

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

We hold 3 real supplement products containing Nadh, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Nadh. Even though Nadh 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 Nadh 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 Nadh
Steady interest

#1,220 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. Nadh is not yet covered by that licensed database, so its write-up cites publicly available medical sources directly (see the references below).
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Nadh reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Nadh 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 Nadh

What is Nadh?

  • Chronic fatigue syndrome
  • Low energy and tiredness
  • Athletic performance
  • Mental clarity and focus
  • Parkinson's disease (investigational)
  • Jet lag

NADH is the active, electron-carrying form of niacin (vitamin B3) that your body uses to make energy in cells. Some people take it as a supplement for fatigue, mental sharpness, and athletic performance, but solid human evidence is limited and mostly preliminary. It appears generally well tolerated in the short term, but talk with your pharmacist or doctor before trying it.

Not applicable (a coenzyme form of vitamin B3/niacin) · Tablets, capsules, sublingual lozenges, sometimes intravenous (clinical settings)

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

Nadh: dosing

There is no official, standardized dose of NADH. Doses used in studies have varied, and product strengths differ from brand to brand. Sublingual (under-the-tongue) forms are marketed as being better absorbed, though strong proof for this is limited.The safest approach is to follow the directions on the product label and not exceed the recommended amount. Taking it earlier in the day may help avoid sleep problems.

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

Read the full Nadh 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 & Nadh

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

0Major
0Moderate
0Minor
2,829No known interaction
2,829 No interaction
No interaction 2,829 drugs checked — show the list

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

Showing the 60 most looked-up of 2,829 medications checked with no known interaction — see the full Nadh list.

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

Nadh References

The 1 sources that drive our Nadh monograph — publicly available pages from reputable medical and government organizations. Every link was verified to work before publishing. Nadh is not covered by the licensed Natural Medicines interaction database, so its page cites these public sources directly.

  1. Niacin - Health Professional Fact Sheet — NIH Office of Dietary Supplements Source

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 Nadh and Levothyroxine Together: Common Questions

Is it safe to take Nadh with Levothyroxine?
We do not list a known interaction between Nadh 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 Nadh 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 Nadh 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 Nadh 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 Nadh in each. That is a conversation for your prescriber, especially if Levothyroxine is being adjusted to a target.
Does Levothyroxine interact with any supplements?
Yes. Levothyroxine has documented interactions with 50 supplements in our database — Nadh 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

Nadh 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 1 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Levothyroxine and Nadh?

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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.