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Cysteine

  • Dietary supplement
  • Varies by country
  • Identity checked
  • Sources last checked 2026-09-04

This page shows what was measured, who it was measured in, and what that does not settle.

What Cysteine does in the body

For the temporary relief of nausea, diarrhea, occasional headache, dizziness or loss of balance, irritability, sneezing, mild back pain or stiffness, or feelings of discomfort or uneasiness.*

Why people take it. For the temporary relief of nausea, diarrhea, occasional headache, dizziness or loss of balance, irritability, sneezing, mild back pain or stiffness, or feelings of discomfort or uneasiness.*

What happened in people

RNAWiki has not yet published a reviewed conclusion for this use.

A fixed RNAWiki sentence

Where this came from

Wording RNAWiki always uses, not a finding about this substance.

No reviewed claim names a result for any goal on this record.

No source is stored against this line.

The limit that matters most

Not recorded.

Where it acts
Not recorded.
Kind of result
No result is published, so no kind of result applies yet
Supervision
Not usually supervised: sold as a supplement or food ingredient where recorded. That is a legal category, not a safety judgement.

What the registries record it as

  • The substance registry classes this as chemical.

    FDA substance registry · K848JZ4886 · read 2026-08-29

  • The supplement label database classes it as amino acid, under the name L-Cysteine.

    NIH Dietary Supplement Label Database · 1135 · read 2026-08-29

Where each sentence above came from

The use the label states, quoted from it. No plain-language version of this sentence has been written.

The use the label states, quoted from it. It is written for a clinician, not for a reader without medical training.

No statement of the main limit is recorded.

The four opening statements run to 67 words.

Words this page uses

Four words worth knowing first

Chosen from what this page shows, with each one explained before the word it depends on.

Formulation

A formulation is the exact made-up form a substance comes in.

A picture of it, and where the picture fails

It is like the difference between a whole bean and instant coffee.

Where that stops being true. Coffee tastes different. A formulation can change how much reaches the blood.

What people get wrong. Two products with the same name are assumed to behave the same. They often do not.

The specific composition and physical form of a product, including salt, excipients and release profile.

What happened in peopleRead from sources, not yet reviewed

What happened in people

Each card is one study: the exact question it asked, who was in it, and whether it showed what it set out to show.

Progression to severe dengue/critical dengue

The study did not show it

Who was studied
NCT07543458
How many people
8800
Study design
Phase 3
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Result not recorded on this page
Repeated elsewhere
Unreplicated

What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.

The limits of this study, and where it came from

Main limit. No limitation is recorded for this study.

How far it carries. This study is recorded from the curated record, not from the registry match.

Form and route.

Interval reported. Not recorded in this summary

Written into the record, not signed off as a reviewed claim.

  • NIH Dietary Supplement Label Database · a recorded source, not a stored snapshot
  • Europe PMC · a recorded source, not a stored snapshot

Major bleeding

The study did not show it

Who was studied
NCT04609111
How many people
6002
Study design
Phase 4
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Result not recorded on this page
Repeated elsewhere
Unreplicated

What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.

The limits of this study, and where it came from

Main limit. No limitation is recorded for this study.

How far it carries. This study is recorded from the curated record, not from the registry match.

Form and route.

Interval reported. Not recorded in this summary

Written into the record, not signed off as a reviewed claim.

  • NIH Dietary Supplement Label Database · a recorded source, not a stored snapshot
  • Europe PMC · a recorded source, not a stored snapshot

Number of Participants With Serious, Adverse, Patient-Centered Events, Including Death, Need for Acute Dialysis, or Persistent Decline in Kidney Function, Comparing Intravenous Sodium Bicarbonate With Intravenous Sodium Chloride.

The study did not show it

Who was studied
NCT01467466
How many people
5177
Study design
Phase 3
Compared against
Not recorded for this study
Kind of result
Living longer, or avoiding a major event
What was found
Result not recorded on this page
Repeated elsewhere
Unreplicated

What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.

The limits of this study, and where it came from

Main limit. No limitation is recorded for this study.

How far it carries. This study is recorded from the curated record, not from the registry match.

Form and route.

Interval reported. Not recorded in this summary

Written into the record, not signed off as a reviewed claim.

  • NIH Dietary Supplement Label Database · a recorded source, not a stored snapshot
  • Europe PMC · a recorded source, not a stored snapshot

Bleeding endpoint

The study did not show it

Who was studied
NCT05125276
How many people
3090
Study design
Phase 4
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Result not recorded on this page
Repeated elsewhere
Unreplicated

What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.

The limits of this study, and where it came from

Main limit. No limitation is recorded for this study.

How far it carries. This study is recorded from the curated record, not from the registry match.

Form and route.

Interval reported. Not recorded in this summary

Written into the record, not signed off as a reviewed claim.

  • NIH Dietary Supplement Label Database · a recorded source, not a stored snapshot
  • Europe PMC · a recorded source, not a stored snapshot

Composite cardiovascular events

The study did not show it

Who was studied
NCT05347069
How many people
2890
Study design
Phase 4
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Result not recorded on this page
Repeated elsewhere
Unreplicated

What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.

The limits of this study, and where it came from

Main limit. No limitation is recorded for this study.

How far it carries. This study is recorded from the curated record, not from the registry match.

Form and route.

Interval reported. Not recorded in this summary

Written into the record, not signed off as a reviewed claim.

  • NIH Dietary Supplement Label Database · a recorded source, not a stored snapshot
  • Europe PMC · a recorded source, not a stored snapshot

Summary Scores on the SUM8 Daily Cough and Phlegm Diary Card On the Morning of Day 4

The study did not show it

Who was studied
NCT01537081
How many people
2810
Study design
Phase 2/Phase 3
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Result not recorded on this page
Repeated elsewhere
Unreplicated

What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.

The limits of this study, and where it came from

Main limit. No limitation is recorded for this study.

How far it carries. This study is recorded from the curated record, not from the registry match.

Form and route.

Interval reported. Not recorded in this summary

Written into the record, not signed off as a reviewed claim.

  • NIH Dietary Supplement Label Database · a recorded source, not a stored snapshot
  • Europe PMC · a recorded source, not a stored snapshot
What we know
RNAWiki holds 6 written-up human studies for this substance, each with the question it asked.
How we know it
Each card names the study, the number of people and what the study set out to measure.
What this does not prove
These summaries were written by a person and have not been signed off as reviewed claims.
Why it matters
A study that failed is as informative as one that worked, and both are here.
What we still do not know
No reviewed claim exists, so no exact population, effect size or interval is published yet.

What is missing or unclearRead from sources, not yet reviewed

Were people like you studied?

RNAWiki cannot tell whether a study fits you. It can show who was in it, and where the result stops carrying.

Who was studied

No description of who was studied is recorded.

Who is missing from the studies

  • Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.

Where the result stopped carrying

  • This is a scope explorer, not a diagnosis engine.
  • It shows who was studied so you can see whether people similar to you were included.

RNAWiki cannot tell whether a study fits you. It can show who was in it.

What it would be like to takeRead from sources, not yet reviewed

Why it might seem to do nothing

A real effect and a noticed effect are different things. These are the recorded reasons the two come apart.

It was studied in different people

The people in the studies were not much like the reader.

On this record: Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.

A different form was studied

The studied form is not the form on the shelf.

On this record: This record is linked to 1 related forms. Evidence does not carry across all of them.

The evidence may simply be wrong

Small early studies often do not hold up.

On this record: RNAWiki has not yet published a reviewed conclusion for this use.

Other reasons RNAWiki checked and found nothing for (10)
It was studied for a different goal
The studies measured something else entirely. Nothing in this record points to this reason.
There was nothing to correct
Where a level is already normal, topping it up may change nothing. Nothing in this record points to this reason.
Something else had to happen too
In the studies it was paired with training, a diet or another treatment. Nothing in this record points to this reason.
The change is too small to feel
A real change can still sit below what a person notices. Nothing in this record points to this reason.
Day-to-day swing hides it
Sleep, food, stress and time of day move most numbers more than this would. Nothing in this record points to this reason.
Not enough time yet
The studies ran longer than the person has waited. Nothing in this record points to this reason.
It was not taken as studied
Missed days change the result, and studies count them. Nothing in this record points to this reason.
Something else changed at the same time
Two changes at once cannot be told apart afterwards. Nothing in this record points to this reason.
The product may not be what it says
Contents of a sold product are not always what the label states. Nothing in this record points to this reason.
No recorded reason
RNAWiki has nothing stored that would explain it. Nothing in this record points to this reason.

None of these is a reason to take more. Taking more is not a step this page ever suggests.

What it would be like to takeRead from sources, not yet reviewed

What taking it involves

The recorded facts about getting hold of it and using it. Nothing here is a suggestion about what you should do.

How it is supplied

Varies by country

Quoted from a source

Where this came from

Copied from a source RNAWiki stored, with the source named.

Read from the recorded approval status.

No source is stored against this line.

Form and route

Not recorded.

Nothing recorded

Where this came from

RNAWiki holds nothing here and says so rather than guessing.

No form or route is recorded.

No source is stored against this line.

Who oversees it

Not usually supervised: sold as a supplement or food ingredient where recorded. That is a legal category, not a safety judgement.

Quoted from a source

Where this came from

Copied from a source RNAWiki stored, with the source named.

The identity record classes it as a supplement ingredient; no medicines register records an approval.

No source is stored against this line.

What is in the pack

Not recorded.

Nothing recorded

Where this came from

RNAWiki holds nothing here and says so rather than guessing.

Nothing is recorded about product quality.

No source is stored against this line.

Where it is registered

Regulatory records are listed in the technical disclosure at the foot of this page.

Counted from records

Where this came from

A count of rows RNAWiki holds. It describes our records, not your body.

Register entries are stored per jurisdiction and shown with their dates.

No source is stored against this line.

Why people stop

Not recorded.

Nothing recorded

Where this came from

RNAWiki holds nothing here and says so rather than guessing.

No record of why people stopped taking it is stored for this substance.

No source is stored against this line.

What it would be like to takeNothing found in the sources checked

What can go wrong

Sorted by where each line came from. A regulator's label and a report somebody sent in are not the same kind of fact.

Nothing found in the sources checked

No harm is recorded against this substance in the sources RNAWiki checked. Finding nothing is not the same as showing there is nothing.

The sources listed were searched and held nothing. That is not the same as nothing existing.

Over a long time. No completed tested study window is recorded, so long-term effects are not established by the registry record.

Groups the studies covered thinly. Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.

What is missing or unclearRead from sources, not yet reviewed

Does the exact form matter?

Evidence belongs to the exact thing that was tested. A different salt, a different mixture or a different preparation is a different question.

The form that was studied

Not recorded.

Nothing recorded

Where this came from

RNAWiki holds nothing here and says so rather than guessing.

The exact form studied is not recorded.

No source is stored against this line.

What is sold

Not recorded.

Nothing recorded

Where this came from

RNAWiki holds nothing here and says so rather than guessing.

Nothing further is recorded about which forms are sold.

No source is stored against this line.

What is recorded as being sold

  • 1 published label names it as an active ingredient. 1 of them describe this substance alone, which is where its own label text on this page comes from.

    US prescribing information · 2061fdfd-1ceb-4c0b-b33a-10ebd30fbef5 · read 2026-08-29

  • Those labels are classed as human otc drug.

    US prescribing information · 2061fdfd-1ceb-4c0b-b33a-10ebd30fbef5 · read 2026-08-29

  • 3457 marketed supplement labels list this ingredient, classed as amino acid/protein and other combinations.

    NIH Dietary Supplement Label Database · 176392 · read 2026-08-29

  • Those labels carry all other, nutrient and structure/function claims. A claim of that kind is written by the manufacturer and is not assessed by any regulator, so its presence says nothing about whether it is true.

    NIH Dietary Supplement Label Database · 176392 · read 2026-08-29

Evidence carries across two names for one substance. It does not carry across a salt, a mirror form or a mixture.

Names and forms linked to this record

What it would be like to takeRead from sources, not yet reviewed

What you could measure

Watching one thing carefully can tell you whether it moved. It cannot tell you what moved it.

This is sold without a prescription, so a person can sensibly watch one thing and see whether it moves.

  1. Pick one goal. One goal only. Two at once cannot be told apart afterwards.

  2. Pick one thing to watch. No registered study lists a measure RNAWiki could read for this.

  3. Measure before you start. Take the same measurement several times first. One reading is not a starting point.

  4. Know the swing. Write down how much it moves on its own across a normal week.

  5. Change one thing. Change nothing else at the same time, including training and sleep.

  6. Give it the study length. No finished study window is recorded, so no length is suggested here.

  7. Track whether you took it. Missed days are the most common reason a home test shows nothing.

  8. Read the trend. Look at the line across weeks. A single reading tells you almost nothing.

What not to measure

  • Anything that swings more day to day than the change you are looking for.
  • A wearable estimate of sleep stages, which is an estimate and not a measurement.
  • Weight on one morning, which mostly records water.
  • A feeling you did not write down before starting.

When to stop

  • Stop if something new and unpleasant starts, and ask a pharmacist or doctor.
  • Stop if you cannot keep everything else steady, because the result will not mean anything.
  • Stop at the end of the window you set, and read the trend then.

Tracking can show whether something changed for you. It cannot show what caused it.

RNAWiki does not work out an amount for anyone.

What is missing or unclearRead from sources, not yet reviewed

What nobody knows yet

Open questions, each with why it is open and what would close it.

How much did people take in the studies?

The sources RNAWiki checked hold nothing for this field.

Why it matters. A result belongs to an amount. Without the amount the result floats free.

What would answer it

A stored source that records it, and a reviewer to sign it off.

Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.

Missing populations

Which groups were under-represented in the studies has not been recorded.

Why it matters. Recorded by the evidence model as a gap on this record.

What would answer it

A study that measures it, and a reviewer to sign it off.

Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.

Missing long-term data

No completed tested study window is recorded.

Why it matters. Recorded by the evidence model as a gap on this record.

What would answer it

A study that measures it, and a reviewer to sign it off.

Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.

No reviewed conclusion

RNAWiki has not yet published a reviewed conclusion for this use.

Why it matters. Recorded by the evidence model as a gap on this record.

What would answer it

A study that measures it, and a reviewer to sign it off.

Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.

Missing interaction studies

No interaction was found in the registers checked. Not finding one is not the same as showing there is none.

Why it matters. Recorded by the evidence model as a gap on this record.

What would answer it

A study that measures it, and a reviewer to sign it off.

Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.

Formulation uncertainty

Several salts, forms or products of Cysteine are recorded. Results from one form may not transfer to another.

Why it matters. Recorded by the evidence model as a gap on this record.

What would answer it

A study that measures it, and a reviewer to sign it off.

Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.

Mechanism not reviewed

No reviewed mechanism story exists for this substance.

Why it matters. Recorded by the evidence model as a gap on this record.

What would answer it

A study that measures it, and a reviewer to sign it off.

Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.

What happened in peopleRead from sources, not yet reviewed

Check any of this yourself

Every line above traced back to the study it came from. This is the technical layer, and the vocabulary changes here.

Where else this substance is registered

FDA substance identifier (UNII)
K848JZ4886

Checks this page had to pass

  • Passed

    Identity resolved

    no open identity hold

  • Passed

    No unresolved merge across substance families

    no quarantine open

  • Passed

    Every public sentence names a source

    The opening statement carries the origin: Quoted from a stored source.

  • Not passed

    Trial roles classified for highlighted evidence

    No registered study is classified as testing this substance.

  • Passed

    No internal keys in reader text

    enforced by the copy-contract test over the rendered page

  • Passed

    Safety mode resolved

    The identity record classes it as a supplement ingredient; no medicines register records an approval.

  • Passed

    Canonical metadata present

    slug and display name present

What is missing or unclearRead from sources, not yet reviewed

What to learn next

Ordered by what would most change how you read this page, starting with what is easiest to misunderstand.

This order is fixed in code and does not count clicks or time on the page.

What is not here

10 questions this page could not answer

These sections were prepared and left out because there was nothing to put in them. They are listed rather than hidden, so the gaps in this record are visible.

  • What was measured, goal by goal — found nothing in the sources checked.
  • How close this is to real life — found nothing in the sources checked.
  • The path through the body — found nothing in the sources checked.
  • Felt, measured, or meaningful — found nothing in the sources checked.
  • How long anything takes — found nothing in the sources checked.
  • What it may clash with — found nothing in the sources checked.
  • Other ways to the same goal — found nothing in the sources checked.
  • Claims that go past the evidence — found nothing in the sources checked.
  • How this medicine reached us — found nothing in the sources checked.
  • What changed on this page — found nothing in the sources checked.

The record as stored

The full record, for auditing

Everything above is built from what is below. This layer keeps the technical vocabulary, record identifiers and every stored row, so a reader who wants to check the page can.

Recorded evidence blocks (6)

On the Cysteine label: indicated for what?

"ELCYS ® is indicated for use as an additive to amino acid solutions to meet the nutritional requirements of newborn infants requiring total parenteral nutrition (TPN); and of adult and pediatric patients with severe liver disease who may have impaired enzymatic processes and require TPN. It can also be added to amino…": indications and usage on Cysteine's label. DailyMed label · 52317b38-b2e6-4a1c-b5b0-43cada0d205e · 2026-04-09

8 registered trials of Cysteine — at which phases?

Registered studies posting no result
8 of 8

8 registered studies of Cysteine: 4 na, 1 early phase1, 1 phase1, 1 phase2, 1 phase3. CLINICALTRIALS_SNAPSHOT · 2026-09-01

98 with a PubMed record

Show the evidence
  • na
    4
  • early phase1
    1
  • phase1
    1
  • phase2
    1
  • phase3
    1
  • completed
    6
1 more recorded row
  • unknown
    2

recorded 2026-09-01 · last checked 2026-09-04

Which 6 trials of Cysteine posted no result?

Posted no result
6 of 6 completed trials
Registrations
NCT00004831, NCT00004940, NCT01921374, NCT02050139, NCT02462746 and NCT04939792
Completion dates
oldest 1998-07; newest 2022-10-31
Show the evidence

Trial

  • NCT00004831
    1998-07
  • NCT00004940
    2001-09
  • NCT01921374
    2014-07
  • NCT02050139
    2015-06
  • NCT02462746
    2016-04
  • NCT04939792
    2022-10-31

At the median, Cysteine's trials enrolled 50 people — anything larger?

Median enrolment
50
Largest enrolment
165
Registered trials counted
8

What do 50 spontaneous reports say about Cysteine — and not say?

These are reports people sent to a regulator. They do not show the medicine caused the reaction. Nobody counted how many people took the medicine and reported nothing. The same event can be reported more than once, and many reports are incomplete. News coverage, lawsuits and new warnings change how often people report. A count is not a rate and not a risk.

Cysteine appears in spontaneous reports to regulators. Across the 1 most-reported reaction term, 50 reaction mentions were counted: parenteral nutrition associated liver disease 50. FAERS via Open Targets · CHEMBL1200630 · 2026-06-24

Show the evidence
  • parenteral nutrition associated liver disease
    50

recorded 2026-06-24 · last checked 2026-09-04

Which reaction does Cysteine's label not list?

parenteral nutrition associated liver disease reported for Cysteine, absent from its label. FAERS via Open Targets · CHEMBL1200630 · 2026-06-24

2 label terms; 1 reported and unlisted; 52317b38-b2e6-4a1c-b5b0-43cada0d205e

Show the evidence
  • parenteral nutrition associated liver disease
    count not stated

recorded 2026-06-24 · last checked 2026-09-04

Where it is registered
Identifiers, relations and other names

The exact record

ChEMBL id
CHEMBL1200630
PubChem CID
23462
CAS number
7048-04-6
RxCUI
221086
InChIKey
XUJNEKJLAYXESH-REOHCLBHSA-N

Relations

Also called
CYSTEINE HYDROCHLORIDE, Cisteina, Cysteinum, E920, E921, acetium, ACETYLCYSTEINE IMPURITY B [EP IMPURITY], CYSTEINE [HSDB], CYSTEINE [II], CYSTEINE [MART.], CYSTEINE [MI], CYSTEINE [VANDF]
Salt form
Cysteine hcl, Cysteine hydrochloride anhydrous, Cysteine hydrochloride monohydrate, L-cysteine hcl, L-cysteine hydrochloride, L-cysteine hydrochloride hydrate
Trade name
Elcys, Nouress
Development code
NSC-755898, E 920, FEMA NO. 3263, NSC-8746
Japanese name
L-cysteine
Sources (5)

Sources

ChEMBL 37 — CC BY-SA 3.0 Unported · ClinicalTrials.gov — US Government work · Open Targets 26.06 — CC0 · mixed register set; per-register licences in docs/specs/corpus-20k-sources.md · openFDA / DailyMed — US Government work

How these records are assembled · Which registers were checked

Index-quality checks
  • identity passed: no open identity hold
  • required summary fields resolved: 3 required field(s) not terminal: Best-supported result, Biggest unanswered question, Human evidence
  • public claims reviewed: 0 reviewed claim(s); drafts are never rendered
  • source coverage passed: 5 source rows
  • no critical contamination: no quarantine open
  • canonical metadata passed: slug and display name present
  • no raw internal fields: enforced by the copy-contract test over the rendered page

This is a record of evidence. It is not medical advice, and it does not say this substance suits you. Nothing here says any substance on RNAWiki is appropriate for a child.