It takes 5 half-lives in order for a substance to decay away to what is considered 0 left. So if you have 500mg in your body and the half life is 1 week, you will have:
Start: 500mg
End of Week 1: 250mg
End of Week 2: 125mg
End of Week 3: 62.5mg
End of Week 4: 31.25mg
End of Week 5: 15.625mg
If you started with only 100mg, divide each week by 5 and you will get much, much lower numbers.
This is why people recommend using Tren-A instead of Tren-E. If you want the side effects to go away fast, Tren-A has a 48 hour half-life (if I remember correctly). So instead of 7 days to cut the amount in half, it is only 2. 5 half-lives is then a scant 10 days, or roughtly 2 weeks. 2 weeks for all the side effects to be completely gone is far better than 5 weeks! Tren - the devil's juice.
