Drug & supplement interaction

L-cysteine + Gabapentin

Gabapentin brand names: Neurontin, Gralise.

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 L-cysteine and Gabapentin 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.

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Interaction report

L-cysteine and Gabapentin

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 Gabapentin and L-cysteine 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.

L-cysteine safety at a glance

L-cysteine overall Use caution Generally well tolerated in food amounts, but the safety of high-dose supplements over time is not well studied.
Pregnancy Likely Safe When used orally in amounts found in foods. There is insufficient reliable information available about the safety of amounts greater than those found in foods;... Read the full pregnancy detail
Breastfeeding Likely Safe When used orally in amounts found in foods. There is insufficient reliable information available about the safety of amounts greater than those found in foods;... Read the full breastfeeding detail

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 Gabapentin and L-cysteine? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Gabapentin

Interactions in our licensed database are recorded against drug classes, not just single drug names. Gabapentin is filed under 4 classifications — including anticonvulsants, cns depressants, oral drugs. L-cysteine has documented interactions with 1 drug class — the most serious being antidiabetes drugs (moderate) — and none of Gabapentin’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

L-cysteine Does Interact With Other Medications

L-cysteine has 86 moderate known drug interactions in our database — Gabapentin isn’t one of them. If you take anything else, check it against the full list below.

Moderate 86 No known interaction 2,744 (incl. Gabapentin)
Taking anything else?

Check Another of Your Medications Against L-cysteine

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

What to actually watch for

What Gabapentin’s Own FDA Label Lists

This is not an interaction — none of it involves L-cysteine. These are the most notable effects listed in the ADVERSE REACTIONS section of Gabapentin’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.

  • Dependence or withdrawal symptoms Worth acting on
  • Thoughts of self-harm Worth acting on
  • Severe muscle breakdown Worth acting on
  • Memory problems Worth acting on
  • Low sodium Worth acting on
  • Unsteadiness Worth acting on
  • Yellowing of the skin or eyes Worth acting on
  • High blood sugar Worth acting on
  • Confusion Worth acting on
  • A severe skin reaction Worth acting on

Showing the 10 most notable of 42 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 Gabapentin. Read the label on DailyMed › Where a percentage is shown, it is the share of 361,481 voluntary FDA FAERS reports for Gabapentin that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. L-cysteine’s licensed record lists no adverse effects our clinical vocabulary could match, so there is no L-cysteine side to compare — that is a limit of the record, not a statement that L-cysteine has no side effects.

Special populations

L-cysteine in Pregnancy & Breastfeeding

Pregnancy And Lactation Likely Safe

When used orally in amounts found in foods. There is insufficient reliable information available about the safety of amounts greater than those found in foods; avoid use. Some research suggests that taking L-cysteine during lactation increases levels of free L-cysteine in breastmilk. However, these levels are lower than those found in some commercial hydrolyzed protein infant formulas.

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

From our Q&A

Questions About L-cysteine or Gabapentin

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers L-cysteine or Gabapentin, 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 Gabapentin

This page covers L-cysteine only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Gabapentin page lists 106 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), Beer (major), Gamma-hydroxybutyrate (ghb) (major) and Kava (major).

By severity: 7 major · 82 moderate · 17 minor.

From our pharmacist’s overview on the Gabapentin page

“Gabapentin (Neurontin, Gralise) calms overactive nerves, which means it already slows your nervous system down, and that is exactly what 78 of the 106 supplements on this list also do. So the dominant risk here is sedation stacked on sedation, extra drowsiness at best and dangerously slowed breathing at worst, and with seven entries ra…”

Reviewed by 2 · Jul 18, 2026

Open the Gabapentin interaction page

One more smart check

Taking L-cysteine as Part of a Dietary Supplement Product? Check It for Interactions

We hold 1 real supplement products containing L-cysteine, each one broken down to its full ingredient list — and combination products often carry several ingredients besides L-cysteine. Even though L-cysteine itself has no known interaction with Gabapentin, 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 L-cysteine and Gabapentin 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 L-cysteine
Steady interest

#1,270 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Gabapentin
Top 5%

#41 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 L-cysteine reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The L-cysteine and Gabapentin 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 L-cysteine

What is L-cysteine?

  • Antioxidant support
  • Skin and hair health
  • Liver support
  • Respiratory and mucus thinning
  • General protein/amino acid supplementation

L-cysteine is a sulfur-containing amino acid your body uses to make proteins and the antioxidant glutathione. Most people get enough from food, and supplements are usually well tolerated, but strong evidence supporting specific health benefits from extra L-cysteine is limited. Talk to your pharmacist or doctor before starting it, especially if you are pregnant, breastfeeding, or have a health condition.

Amino acid (not a plant part) · Capsules, tablets, powder; also available as N-acetylcysteine (NAC)

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

L-cysteine: dosing

There is no official standardized dose of L-cysteine established for general supplement use. Products vary widely in strength, and much of the dosing research actually involves NAC rather than plain L-cysteine.The safest approach is to follow the directions on the product label and not exceed the recommended amount. Higher doses have not been well studied and may increase the risk of side effects.

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

Read the full L-cysteine monograph & all interactions
Medication

About Gabapentin

What Is Gabapentin Used For?

Brand names: Neurontin, Gralise

Gabapentin (brands include Neurontin, Relgaabi, Gabarone, Gralise, and Horizant) is primarily used to manage postherpetic neuralgia (PHN) — the nerve pain that lingers after a shingles outbreak — in adults. Neurontin, Relgaabi, Gabarone, and gabapentin capsules, tablets, and oral solution are also used as add-on therapy for partial onset seizures (a type of epilepsy) in adults and children aged 3 and older.

Horizant (gabapentin enacarbil extended-release tablet) has two specific approvals: treatment of moderate-to-severe primary restless legs syndrome (RLS) in adults, and management of postherpetic neuralgia in adults. Horizant is not recommended for people who need to sleep during the day and stay awake at night. Gralise is approved only for postherpetic neuralgia and cannot be substituted for other gabapentin products due to its different release profile.

Most-Reported Side Effects for Gabapentin

From FAERS, the FDA’s public side-effect reporting system (361,481 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Fatigue 24,972 reports
Nausea 22,728 reports
Diarrhea 18,114 reports
Headache 17,897 reports
Dizziness 16,238 reports
See full Gabapentin drug information
Keep checking

Other Drugs & L-cysteine

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

0Major
86Moderate
0Minor
2,743No known interaction
86 Moderate 2,743 No interaction
Moderate

86 interactions

Showing 60 of 86 moderate interactions — see all 86 on the L-cysteine page.

No interaction 2,743 drugs checked — show the list

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

Showing the 60 most looked-up of 2,743 medications checked with no known interaction — see the full L-cysteine list.

See the full L-cysteine interactions page
See every supplement checked against Gabapentin, ranked by severity
Evidence & sources

L-cysteine References

The 2 references that drive our L-cysteine 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. Dowlati Y, Maheux M, Meyer JH. The effect of oral L-cysteine on breast milk and plasma cysteine concentrations. Neuropsychiatr Dis Treat 2020;16:3163-3172.
  2. Lee S, Han KH, Nakamura Y, et al. Dietary L-cysteine improves the antioxidative potential and lipid metabolism in rats fed a normal diet. Biosci Biotechnol Biochem 2013;77(7):1430-4.

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 L-cysteine and Gabapentin Together: Common Questions

Is it safe to take L-cysteine with Gabapentin?
We do not list a known interaction between L-cysteine and Gabapentin. 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.
How was the L-cysteine and Gabapentin combination checked?
Interactions in our licensed database are recorded against drug classes. Gabapentin is filed under 4 classifications, and L-cysteine has documented interactions with 1 drug class — none of Gabapentin'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 L-cysteine interact with any other medications?
Yes. L-cysteine has 86 documented drug interactions in our database — Gabapentin 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 Gabapentin interact with any supplements?
Yes. Gabapentin has documented interactions with 106 supplements in our database — L-cysteine is not one of them. The Gabapentin 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

L-cysteine monograph Uses, safety profile, and every drug interaction in one place Gabapentin drug information The full plain-English guide to this medication Gabapentin supplement interactions Every supplement checked against Gabapentin, 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 Gabapentin and L-cysteine?

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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.