Herb & supplement monograph

Acetyl-l-carnitine Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Acetyl-l-carnitine interacts with medications. The heart of this page is the interaction list — every drug Acetyl-l-carnitine is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Acetyl-l-carnitine is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Interaction report

Drugs that interact with Acetyl-l-carnitine

203 medications have a known interaction with Acetyl-l-carnitine, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Acetyl-l-carnitine using our pharmacist-reviewed interaction data.

AI summaries are generated from our Acetyl-l-carnitine interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction 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.
Possible. 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
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Acetyl-l-carnitine combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Acetyl-l-carnitine affects

Every type of medication (drug category) Acetyl-l-carnitine is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 4 drug categories Acetyl-l-carnitine interacts with

Acenocoumarol (sintrom)Serotonergic DrugsThyroid HormoneWarfarin (coumadin)

Acenocoumarol (Sintrom)

Theoretically, acetyl-L-carnitine might increase the anticoagulant effects of acenocoumarol.
L-carnitine, the parent compound of acetyl-L-carnitine, might enhance the anticoagulant effects of acenocoumarol, an oral anticoagulant that is similar to warfarin, but shorter-acting. There are at least two case reports of INR elevation when L-carnitine was taken with acenocoumarol. In one case, a 33-year-old male with a previously stable INR had an elevated INR of 4.65 after L-carnitine was started and continued for 10 weeks. INR normalized after discontinuation of the L-carnitine-containing product. It is unclear if such an interaction would also occur with acetyl-L-carnitine.

Likelihood Possible Evidence D

Serotonergic Drugs

Theoretically, acetyl-L-carnitine might increase the risk of serotonergic side effects, including serotonin syndrome and cerebral vasoconstrictive disorders, when taken with serotonergic drugs.
Animal research shows that acetyl-L-carnitine can increase levels of serotonin in the brain.

Likelihood Possible Evidence D

Thyroid Hormone

Theoretically, acetyl-L-carnitine might decrease the effectiveness of thyroid hormone replacement.
L-carnitine appears to act as a peripheral thyroid hormone antagonist by inhibiting entry of thyroid hormone into the nucleus of cells. Taking L-carnitine also seems to diminish some of the symptoms of hyperthyroidism. It is unclear if such an interaction would occur with acetyl-L-carnitine.

Likelihood Probable Evidence B

Warfarin (Coumadin)

Theoretically, acetyl-L-carnitine might increase the anticoagulant effects of warfarin.
L-carnitine, the parent compound of acetyl-L-carnitine, might increase the anticoagulant effects of acenocoumarol, a shorter-acting oral anticoagulant similar to warfarin. There is not enough information to know whether this interaction occurs with acetyl-L-carnitine and warfarin.

Likelihood Possible Evidence D

Monograph

Acetyl-l-carnitine: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Acetyl-L-carnitine is a form of the amino acid carnitine that the body uses to help produce energy in cells. It is most studied for nerve pain and memory-related conditions, though the evidence is mixed and often limited. It is generally well tolerated for short-term use, but you should talk with your pharmacist or doctor before starting it.

Part used: Not applicable (a naturally occurring compound made in the body)
Common forms: Capsules, tablets, powder, and liquid

People commonly use it for

Memory and cognitive support
Nerve pain (neuropathy)
Energy and fatigue
Age-related decline
Male fertility
Mood support

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Generally well tolerated short-term, but long-term safety is not fully established.

PregnancyInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full pregnancy detail

BreastfeedingInsufficient reliable information

Insufficient reliable information available; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Jump to a section

Overview

Acetyl-L-carnitine (often shortened to ALCAR) is a form of carnitine, a substance the body naturally makes from the amino acids lysine and methionine. Your body uses carnitine to help turn fat into energy inside your cells. Acetyl-L-carnitine is the "acetylated" form, which means it may cross into the brain more easily than plain L-carnitine.

Because it is made in the body, it is not an herb and does not come from a plant. As a supplement, it is produced in a lab and sold as capsules, tablets, powders, and liquids. People take it hoping to support brain function, energy, nerve health, and healthy aging.

How it works

Inside cells, carnitine helps carry fatty acids into the mitochondria, the part of the cell that produces energy. By supporting this process, carnitine may help cells make energy more efficiently.

The acetyl group attached to this form may allow it to reach the brain and nerve tissue more easily. Researchers think it may also support the production of certain brain chemicals and help protect nerve cells from damage. Many of these ideas come from laboratory and animal studies, so they do not always translate directly to benefits in people.

Effectiveness

Does Acetyl-l-carnitine work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 39 uses evaluated

5 Possibly effective 1 Leans ineffective 33 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

Possibly Effective Age-related cognitive decline