A missed or late dose increases the risk of resistance

Drug levels with good adherence

Drug doses are calculated so that average drug levels are high enough to be active against HIV without risking resistance — 24 hours a day — and low enough to minimise the risk of side effects.

Missing or being late with a drug lets the drug levels fall to a level where resistance can develop.

The more often you are late or miss a dose, the greater the chance this will occur.