Understanding Half-Lives

What is a half-life?#

A half-life is the time it takes for half of a substance to be eliminated from your body. If a compound has a 4-hour half-life and you inject 500 mcg, after 4 hours you'll have roughly 250 mcg active. After another 4 hours, 125 mcg. This exponential decay continues until the compound is essentially cleared.

Why it matters for dosing#

Half-life determines how often you need to dose. Short half-life compounds (like BPC-157 at 4 hours) need multiple daily doses to maintain consistent levels. Long half-life compounds (like semaglutide at 168 hours / 7 days) only need weekly dosing.

A compound is considered ~97% cleared after 5 half-lives. For BPC-157, that's about 20 hours. For semaglutide, that's 5 weeks.

Dose stacking#

When you take another dose before the previous one is fully cleared, levels stack. This is normal and expected for most protocols. With BPC-157 dosed twice daily, your second dose adds on top of whatever remains from the first. Over several days, you reach a steady state where intake equals elimination.

Practical implications#

Use the Compound Levels screen to visualize your actual stacking patterns. If you notice a compound isn't working well, check whether your dosing interval matches the half-life. Too infrequent dosing of short half-life compounds leads to peaks and valleys that may reduce effectiveness.