Drug & supplement interaction

L-cysteine + Daratumumab

Daratumumab brand name: Darzalex.

No Known Interaction
Medically reviewed by · Updated June 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between L-cysteine and Daratumumab 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.

Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

L-cysteine and Daratumumab

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 Daratumumab 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 Daratumumab and L-cysteine? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
Keep it in perspective

L-cysteine Does Interact With Other Medications

L-cysteine has 86 moderate known drug interactions in our database — Daratumumab 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. Daratumumab)
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 Daratumumab’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 Daratumumab’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. 6 of them are worth acting on rather than waiting out — marked below.

  • Dehydration Worth acting on
  • A low white blood cell count Worth acting on mentioned in 4.9% of FDA reports for Daratumumab
  • A low platelet count Worth acting on
  • Anemia Worth acting on
  • Shortness of breath Worth acting on
  • A higher chance of infection Worth acting on mentioned in 5.0% of FDA reports for Daratumumab
  • Numbness or tingling mentioned in 3.7% of FDA reports for Daratumumab
  • Cough
  • Fever
  • Constipation

Showing the 10 most notable of 14 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 Daratumumab. Read the label on DailyMed › Where a percentage is shown, it is the share of 42,488 voluntary FDA FAERS reports for Daratumumab 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

Overlapping uses

What Daratumumab Is Prescribed For, and What L-cysteine Has Been Studied For

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

Daratumumab is prescribed for: Darzalex is approved for adult patients with multiple myeloma. It can be used in newly diagnosed patients who are not candidates for a stem cell transplant, in newly diagnosed patients who are eligible for a stem cell transplant (when used with certain combination regimens), and in patients whose myeloma has returned or stopped responding to earlier treatments. Depending on how far the disease has progressed and which medicines a patient has tried before, Darzalex may be given alone or combined with other drugs such as lenalidomide, bortezomib, thalidomide, carfilzomib, pomalidomide, melphalan, and dexamethasone. Each combination has its own specific set of criteria — your oncologist will determine which regimen fits your situation.

L-cysteine has been studied for:

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

    L-cysteine for cancer

    Although there is interest in using oral L-cysteine for prevention of cancers of the upper gastrointestinal tract, there is insufficient reliable information about the clinical effects of L-cysteine 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 Daratumumab on your own; if you are taking L-cysteine for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

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 Daratumumab, 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 Daratumumab 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

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

29 days ago today
Medication Daratumumab
Steady interest

#2,330 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 20, 2026. The L-cysteine and Daratumumab 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 Daratumumab Injection

What Is Daratumumab Injection Used For?

Brand name: Darzalex

Darzalex is used to treat adult patients with multiple myeloma (a cancer of plasma cells in the bone marrow). It is used in several different settings: for people newly diagnosed who cannot have a stem cell transplant, for those who are eligible for a stem cell transplant, and for those whose myeloma has come back or stopped responding to earlier treatments.

Darzalex can be used alone or in combination with other medicines such as lenalidomide, bortezomib, pomalidomide, carfilzomib, thalidomide, melphalan, prednisone, and/or dexamethasone. The specific combination depends on where a patient is in their treatment journey and which prior therapies they have received.

Most-Reported Side Effects for Daratumumab

From FAERS, the FDA’s public side-effect reporting system (42,488 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Plasma cell myeloma 3,971 reports
Infusion related reaction 2,703 reports
Pneumonia 2,104 reports
Neutropenia 2,097 reports
Fatigue 1,962 reports
See full Daratumumab Injection 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 Daratumumab, 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 Daratumumab Together: Common Questions

Is it safe to take L-cysteine with Daratumumab?
We do not list a known interaction between L-cysteine and Daratumumab. 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.
Are L-cysteine and Daratumumab 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 L-cysteine in each. That is a conversation for your prescriber, especially if Daratumumab is being adjusted to a target.
Does L-cysteine interact with any other medications?
Yes. L-cysteine has 86 documented drug interactions in our database — Daratumumab is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.

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 Daratumumab Injection drug information The full plain-English guide to this medication Daratumumab supplement interactions Every supplement checked against Daratumumab, 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 Daratumumab and L-cysteine?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

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.