Astragalus

Supplements · Immune & Antimicrobial Herbs · Supplement, Typed Supps

A traditional Chinese root studied for immune support — the evidence so far is weak.

Stage by stage

Intake (Extract capsule or root): Active polysaccharide compounds absorbed in the small intestine.
Small intestine (Absorbed): Absorbed alongside other plant compounds.
Bloodstream (Interacts with immune cells): Circulates and interacts with immune cell activity.
Immune function (Studied over consistent use): Studied for supporting immune cell activity, generally with consistent use over time rather than acute dosing.

What the evidence supports

Improving immune function — insufficient evidence. Most supporting trials are small, of poor methodological quality, and conducted in one region, so a genuine immune benefit in healthy people is not established.
Reducing exercise-induced dips in immunity in heavily-training athletes — limited evidence. A small number of controlled trials suggest an effect, but the evidence is preliminary.

Typical dose

Doses vary widely between traditional decoctions and standardised extracts, and no single trial-backed dose is well established

Upper limit: No established UL

Timing

With food, standard dosing.

Time to effect

Weeks: Consistent use for any reported immune effect in studies.

Medication interactions

Immunosuppressants (e.g. ciclosporin, tacrolimus, corticosteroids): Its immune-stimulating action may work against drugs meant to suppress the immune system. (moderate)

Common myth

“Astragalus is best used only when you’re already sick.” In reality: Most of its traditional and studied use is preventive and ongoing, rather than as a treatment once illness has started.