Medication Half Life Calculator

Estimate drug clearance time based on half-life and doses taken.

Half-Life (hours)

Last Dose (mg)

Clearance Target (%)

Formula

Hours = (ln(1 - Target%/100) / ln(0.5)) x Half-Life

How many half-lives does it take to clear a drug?

It takes about 5 half-lives to clear approximately 97% of a drug from the body.

What affects drug half-life?

Liver function, kidney function, age, and body composition all affect half-life.

Does half-life determine dosing frequency?

Yes, drugs with shorter half-lives generally need to be taken more frequently.

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