SHEET /m/cysteine · PubChem CID 5862 · CAS 52-90-4 · REV 2026.07
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Cysteine from source
C3H7NO2S · 121.16 g/mol
L-cysteine · Cystein · Thioserine · Half-cystine
sulfur-containing amino acid
CategoryBody
Fig. 1 · 2D structure RDKit
C([C@@H](C(=O)O)N)S
Where you'll find it
Not yet mapped to everyday foods or products.
The dose makes the poison inferred
A reported rat oral LD50 for Cysteine is 1,890 mg/kg, the dose lethal to half the animals tested. Scaled by body mass alone:
132.3 g
a median lethal dose scaled to 154 lb (132,300 mg)
“The dose makes the poison” is a cross-species estimate shown as neutral science, not a threshold anyone should act on. Real toxicity depends on the person, not body mass alone.
Toxicity & hazards
Toxicity · LD50
1,890 mg/kg · low toxicity · LD50 rat oral from source
The dose lens above scales this to a body weight.
3 more reported values
- 1,550 mg/kgLD50 · other · rat
- 1,620 mg/kgLD50 · other · rat
- 2,000 mg/kgLD50 · dermal · rat
WarningIrritantH302, H315, H319, H335from source
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