Dosing frequency for Testosterone Replacement Therapy (TRT) is very important. The goal of dosing your treatment is to mimic the body's natural production the best we can. A young, healthy male without low testosterone (hypogonadism) will secrete around 10mg of testosterone naturally every night to be used throughout the day. In order to decide on frequency dosing of testosterone, we must first understand a few things discussed below.
What is a drug's half life?
The half-life of a drug is the time it takes for the amount of a drug's active substance in your body to reduce by half. For example, if one takes a dose of 100mg of a drug, and its half-life is 8 days, that means by day 8, 50mg will be left in the body.
Testosterone cream has a half-life of 12 hours, which is why this form of testosterone is to be taken twice daily (morning and evening) to maintain appropriate levels. So, the dose you take at 8am, there will only be about half of it left at 8pm in your body, which is why one would take it again at 8pm...to maintain a steady level.
In regards to injectable, testosterone cypionate, the half-life is 8 days. After you inject a dose, the serum blood levels rise and peak around days 3-4 and then will start to decline from there. I recommend my patients inject on day 1 and then again on day 4 of the week in split doses. So, when testosterone levels peak on day 3-4 and it would normally begin to decline after that, another dose is administered on day 4 to maintain a more steady testosterone level. For example, if I want a man to take 100mg of testosterone cypionate weekly, I will have him inject 50mg on day 1 and then another 50mg again on day 4.
There are some instances where a patient may need to inject more frequently than twice weekly. This is due to having a low SHBG level. Not all men will have a low SHBG level. To understand why one would inject even more frequently, one must understand what SHBG is and it's role in testosterone regulation. See my blog post, "What is Sex Hormone-Binding Globulin & What is its Role in the Body? " https://www.elitetrtclinic.com/post/what-is-sex-hormone-binding-globulin. Basically, if you have a low SHBG level, you are not able to bind very much testosterone; therefore, causing a high free testosterone level and potential side effects with higher, less frequent dosing. When we give testosterone in tiny doses ("micro-doses") when one's SHBG level is low, we have better control over your testosterone levels to prevent unwanted side effects.
I have seen many providers out there that will prescribe testosterone cypionate to be injected once every 2 weeks. This protocol ends up chemically castrating a man when you understand that the drug half-life is 8 days. Injecting every 2 weeks after the first dose causes the testosterone levels to drop down very low before injecting again causing a "yo-yo" affect. So, injecting once, every two weeks is no where near mimicking the body's natural secretion rhythm and men end up not feeling well on this type of protocol because the body wouldn't normally secrete testosterone every 2 weeks.
