1. What is an Ester?
Testosterone in its raw state has a half-life of less than 1 hour. To make it usable for therapy, we attach an "ester" (a carbon chain) to the 17-beta hydroxyl group of the testosterone molecule.
The Rule of Thumb: The longer the carbon chain, the less water-soluble and more lipid-soluble the drug becomes. This means it sits in the muscle depot longer, slowly releasing into the bloodstream as enzymes cleave off the ester.
2. Half-Life Comparison Chart
Understanding these release times is critical for maintaining stable blood levels and minimizing side effects like acne or mood swings derived from hormonal fluctuations.
Active Half-Liver (Days)
*Note: Biological half-life varies by individual metabolism.
3. The "Esther Weight" Factor
This is the most overlooked factor in dosing. When you inject 100mg of Testosterone Enanthate, you are not getting 100mg of Testosterone. You are getting Testosterone + Example. The ester takes up weight in the solution.
- Testosterone Suspension: 100mg = 100mg Testosterone (No ester)
- Testosterone Propionate: 100mg = ~83mg Testosterone
- Testosterone Enanthate: 100mg = ~72mg Testosterone
- Testosterone Cypionate: 100mg = ~70mg Testosterone
This explains why "Propionate" often "feels" stronger mg-for-mg compared to Cypionate; there is actually more active hormone per milliliter because the ester chain is lighter.
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