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1. ## Confused about half lives

Ok, I think I understand the basic concept of a half life. It is essentially the time at which only half of the gear remains active in the body. I am still confused, however, when it comes to the practical application of this. Does this mean that at day one I have all of the injected gear in my blood, and this tapers off at the half-life rate? For the quick acting esters, this makes sense to me, but aren't the long-lasting esters kept somewhat inactive in the muscle until they are slowly absorbed into the blood? So wouldn't this mean that the blood concentration the day after an injection of long-acting ester (like enanthate ) is very little, and then the blood concentration slowly increases to half of the original dose, and then decreases again to zero? As you can see I'm very confused. Can someone please give me an example and show me what my blood concentrations would be and how they did the calculations with the following cycle (see below)? I've tried to figure it out on my own, but just can't seem to get it right. And don't just make fun of me and tell me to research it. I have looked everything up and I'm just plain confused.

Weeks 1-4 propionate
Weeks 1-10 enanthate

2. Let me have a go

Basically, and u already know this, the length of a half life is the time it takes for a steroid ester to release half of the compound into your blood stream. So if Prop has a half life of 5 days and you inject 100 mg on day 1, by day 6, 50 mg of that would have entered your bloodstream. By day 11, another 25 mg would enter your bloodstream (half of the inactive unreleased compound on day 6)....so it'll look something like this:

Day 1 100mg injected/ Inactive, 0mg released
Day 6 50mg inactive , 50mg released
Day 11 25mg inactive , 25mg released
Cumulative at day 11: 75 mg released, 25 mg inactive

In the case of enanthate , with a halflife of 10 days, the days in the example will be Day 1, Day 11, and Day 21 instead of 1,6,11 for the prop.

What gets complicating is that just because it released doesnt mean its "active", that would depend on the number of receptor sites in your muscle tissue...if you're genetically predisposed to have alot, then the amount released gets used up right away. If you have a few receptor sites, then saturation is reached quickly and you have released but unused quantities circulating in your blood stream. That is why some people need only a small qty of AS to be effective (too much will just cause too many sides) and others must take truckloads to see results while still experiencing minor sides (esp those who have used HGH to get big through hypertrophy, or increase is muscle cells, because their receptor sites increase alongside). Excess circulating steroid is also why alot of ppl opt for clenbuterol immaediately after a cycle: the increased blood flow and body temperature accelerates the receptor site's uptake of the circulating steroid. Different people have diff ratio of receptor sites and thats why different compounds work different in each of us...Anadrol does not work as well for as dbol does, and vice versa for the other person.

A last interesting nugget is that if you look at half life of a compound...the rate of release from the muscle into the blood is highest in the first day after the injection. It slows down afterwards because , visually speaking, on a graph, if you keep on halfing a variable at set increments, the slope is steepest in the beginning and levels off as you go along. However, there is a cumulative effect as the muscle slowly takes up the steroids and becomes saturated. Hope this helps

cheers
Last edited by InsaneInTheMembrane; 03-04-2004 at 12:24 AM.

3. a half life is a term that can apply to anything. It can apply to anything that has a rate of change that follows this equation X=P(0.5)^t where P is the initial amount, X is the amount changed in some way, and t is the number of half lives that have gone by in time.

The amount in your blood does not follow this math. That is because there is a rate of steroid release from muscle and a rate of steroid breakdown of blood steroids . There are two competing reactions, and they may of may not add up to give blood levels which follow the pattern of a half life.

4. I'm glad someone posted this. I understand a little better now.

5. Yeah...great inof so far guys. Lets say that I want to calculate the amount released into my bloodstream at 2, 5, or 8 days after injection (with a 10 day half life)? Is there like an equation to determine such days in between half lives?

6. Yes theres a way, Its just a slightly different permutation of the formula proposed by Brokenbricks...also, I must agree with him on his point...my explaination was maybe a bit simplistic but i had to simplify cuz Dilatory was somewhat confused.

X = P / 2^(d/H) where:

X = residual amount (unreleased)
P = initial Amount (in mg)
d = # of days elapsed after injection
H = designated half life

so with a 200mg injection of Enanthate (10 day halflife), after 3 days:
X = 200 / 2^(3/10) = 162 mg unreleased
you substract this number by the init amt (200 - 162), you get 38mg released

7. What then, are half lives calculated from? In vitro?