Common (>10% users):

• None considered clinically meaningful at 60-180 mg/day.
• Slight herbal aftertaste / mild dyspepsia if taken without food (eliminated by taking with breakfast/lunch).

Less common (1-10%):

• Mild GI upset (heartburn, nausea, loose stool) — usually if taken without food or at >200 mg/day.
• Subjective "wired" or mild stimulation in a small minority — not stimulant-class but reported anecdotally; unclear mechanism.

Rare-serious (<1%):

• Hepatotoxicity at very high doses. In-vitro EC50 in human hepatocytes ~95 μM (Aruoma 2012, PMID 22531045); rats at 600 mg/kg/day showed liver and myocardial damage; subchronic 30-day rodent studies showed AST elevations at high doses. At 60-180 mg/day in humans, no clinical hepatotoxicity has been reported, and CA is GRAS as a food preservative. Watch ALT/AST at any sustained dose >300 mg/day pure CA.
• CYP3A4 induction at high doses — CA induces CYP3A4 and CYP2B6, inhibits CYP2C9 and CYP3A4 in vitro at high concentrations. Clinical relevance at supplement doses is likely minimal but flag for narrow-therapeutic-index drugs (statins, certain antiarrhythmics, hormonal contraceptives, immunosuppressants). See §Drug interactions.
• Theoretical pro-oxidant flip at supraphysiological doses. The quinoid form can become pro-oxidant if cellular glutathione is depleted. Practical relevance: do not stack with chronic glutathione-depleting agents (high-dose acetaminophen, heavy alcohol — neither relevant to the user).
• Allergic reactions / contact dermatitis — extremely rare; most reports are with topical rosemary essential oil (different chemistry). Oral CA at supplement doses has essentially no allergy literature.
• Theoretical uterine stimulation / pregnancy concern — rosemary extract has traditional use as an emmenagogue. CA itself does not have direct uterotonic data, but the standardized rosemary extract category is generally avoided in pregnancy as a precaution. Not relevant to the user; flag for any female user planning conception.

Specific watch periods: None at 60-180 mg/day. Baseline + 8-12 week ALT/AST + GGT only if dosing >200-300 mg/day pure CA chronically.