T Nation

Test Cyp Half Life and EOD Injections


#1

I have a couple of questions about Test Cyp half life and its implications for an EOD injection protocol:

Is 7-8 days really the correct half-life of Testosterone Cypionate?
Is this half-life affected by the volume of the dose? For example, if you're dosing at 25mg EOD instead of 100mg every 7-8 days, does the 25mg reach its half-life (12.5mg) at approximately 7-8 days?

Assuming that this half-life is correct and that it is the same for smaller dosages, does this mean that with an EOD protocol, at any given time you basically have 4 doses of test that are working their way from peak concentration to half-life (and at least another 4 on their way from half-life to zero)?

To use the 25mg example, if you assume ~1.5-2mg decline per day on average from the time of injection (a rough estimate--the decline is of course not even from day to day), you would be looking at steady levels of ~70-90mg active in the system at all times (between the present dose, the three doses working their way from 25mg down to 12.5, and other doses still working their way down from half-life to zero.

Finally--are there any potential negative effects to such overlapping doses? Do you lose any desirable effects (from a TRT standpoint) as a result of not having any big front-load of testosterone? Or is this precisely what's desirable to keep levels most stable?

Thanks,

JM


#2

yes, no, yes (that's what half life means), no, no, yes


#3

Thanks.

I found the following calculator online for estimating Test levels with overlapping injections:

http://pct.befit4free.net/index.php

IF you plug in 25mg and a 360-day 'cycle' (the tool was built for steroid users), it shows that it takes about a month to come close to the peak sustained by such a regimen (130mg test in system), and two months to achieve complete stability.

In light of this, would it make sense to front-load with a larger dosage? If I'm doing the math on this correctly, then front-loading with 100mg and then continuing normally with 25mg dosages would jack Test present in the body up above 100mg immediately and then increase slowly with growing stability. Are there any downsides to this from a TRT stand point?


#4

Ive never understood why people make this stuff so god damned complicated...inject 50 mg twice a week if you need 100 mg/week...use 150 mg for your first shot....this isn't rocket science


#5

It may not be rocket science but it is sure interesting to me. I had never fully thought about the Half life of my Testosterone cypionate.
I use a 3 time a week schedule for my injections. A week has 168 hours, divide that by 3 = 56 hours.
Monday 6:00 AM
Wednesday 2:00 PM
Friday 10 PM
I use 200 MG/ML and inject 20 ML, which gives me a dose of 40 MG of Testosterone each time. I derived a degradation rate for Testosterone cypionate of 8.67%.
I then ran a model for this protocol.


#6

1 Monday 40.00
2 Tuesday 36.53
3 Wednesday 73.36
4 Thursday 67.00
5 Friday 101.19
6 Saturday 92.42
7 Sunday 84.41
8 Monday 117.09
9 Tuesday 106.94
10 Wednesday 137.67
11 Thursday 125.73
12 Friday 154.83
13 Saturday 141.41
14 Sunday 129.15
15 Monday 157.95
16 Tuesday 144.26
17 Wednesday 171.75
18 Thursday 156.86
19 Friday 183.26
20 Saturday 167.37
21 Sunday 152.86
22 Monday 179.61
23 Tuesday 164.03
24 Wednesday 189.81
25 Thursday 173.36
26 Friday 198.33
27 Saturday 181.13
28 Sunday 165.43
29 Monday 191.08
30 Tuesday 174.52
31 Wednesday 199.39
32 Thursday 182.10
33 Friday 206.31
34 Saturday 188.42
35 Sunday 172.09
36 Monday 197.17
37 Tuesday 180.07
38 Wednesday 204.46
39 Thursday 186.73
40 Friday 210.54
41 Saturday 192.29
42 Sunday 175.62
43 Monday 200.39
44 Tuesday 183.02
45 Wednesday 207.15
46 Thursday 189.19
47 Friday 212.79
48 Saturday 194.34
49 Sunday 177.49
50 Monday 202.10
51 Tuesday 184.58
52 Wednesday 208.58
53 Thursday 190.49
54 Friday 213.98
55 Saturday 195.43
56 Sunday 178.48
57 Monday 203.01
58 Tuesday 185.41
59 Wednesday 209.33
60 Thursday 191.18
61 Friday 214.61
62 Saturday 196.00
63 Sunday 179.01
64 Monday 203.49
65 Tuesday 185.85
66 Wednesday 209.73
67 Thursday 191.55
68 Friday 214.94
69 Saturday 196.31
70 Sunday 179.29
71 Monday 203.74
72 Tuesday 186.08
73 Wednesday 209.94
74 Thursday 191.74
75 Friday 215.12
76 Saturday 196.47
77 Sunday 179.43
78 Monday 203.88
79 Tuesday 186.20
80 Wednesday 210.06
81 Thursday 191.85
82 Friday 215.21
83 Saturday 196.55
84 Sunday 179.51
85 Monday 203.95
86 Tuesday 186.27
87 Wednesday 210.12
88 Thursday 191.90
89 Friday 215.26
90 Saturday 196.60
91 Sunday 179.55
92 Monday 203.99
93 Tuesday 186.30
94 Wednesday 210.15
95 Thursday 191.93
96 Friday 215.29
97 Saturday 196.62
98 Sunday 179.58
99 Monday 204.01
100 Tuesday 186.32
101 Wednesday 210.17
102 Thursday 191.94
103 Friday 215.30
104 Saturday 196.64
105 Sunday 179.59
106 Monday 204.02
107 Tuesday 186.33
108 Wednesday 210.17
109 Thursday 191.95
110 Friday 215.31
111 Saturday 196.64
112 Sunday 179.59
113 Monday 204.02
114 Tuesday 186.33
115 Wednesday 210.18
116 Thursday 191.96
117 Friday 215.31
118 Saturday 196.65
119 Sunday 179.60
120 Monday 204.03
121 Tuesday 186.34
122 Wednesday 210.18
123 Thursday 191.96
124 Friday 215.32
125 Saturday 196.65
126 Sunday 179.60
127 Monday 204.03
128 Tuesday 186.34
129 Wednesday 210.18
130 Thursday 191.96
131 Friday 215.32
132 Saturday 196.65
133 Sunday 179.60


#7

Im not sure where your model breaks down, but if you're injecting 120 mg/week, your max levels should approach somewhere around double that...


#8

Correction: your max levels should approach about 194 with 7 day half life. Your decay constant is 1.2599. Your serum levels will be between 154 and 194 throughout the week.


#9

I thought that also, but the model does not show that. I know I have some error in that I used a contestant degradation factor, because after 90 days the original dose becomes inert. After comparing my model to the online Calculator I came to trust its data, but without the formal you never really know. I ran 4 different models for T cypionate. The wave is difference between peek amount of T Cyp. and the lowest amount during the cycle. The cycle being the number of days, not the total length because TRT is ongoing.

Miligrams Of T cyp 200 100 50 33
Days 14 7 3.5 2.33
Wave 192.3 89.6 37.5 28.5
Max Dose 266.6 200 170.7 158.7