How long does amoxicillin stay in your system after you take it? I guess the active life in hours? (how long would it cause side effects).

Varies by dose and… if other (interacting) meds/supplements R being taken. Half-life is 61.3 min; 60% of the dose is excreted in urine 6-8 hrs after dose. Generally a med is cleared from the system within 10 half-live, thus about 10 hours. Other meds may prolong its presence in the body; so side effects may last longer. Depending on what side effects U R having, U may need to seek medical help quickly (swollen throat.