I asked aristotle.science which was better: SubQ or IM shots for testosterone. SubQ was the answer. If you’re currently using TRT which do you prefer and why?
The Core Finding: SubQ Shows Potential Advantages
A 2022 study in The Journal of Urology comparing 234 hypogonadal men treated with intramuscular testosterone cypionate versus subcutaneous testosterone enanthate (both at 100 mg weekly) found that subcutaneous injection was associated with lower post-therapy estradiol and hematocrit levels compared to intramuscular injections. The researchers concluded that subcutaneous testosterone “represents an effective testosterone delivery system with a potentially preferable safety profile over intramuscular testosterone cypionate”.
This matters clinically because:
Elevated hematocrit is the most common reason men must reduce TRT dose or donate blood
Elevated estradiol is the most common reason men are prescribed aromatase inhibitors they may not need
Head-to-Head Comparison
Parameter
Subcutaneous
Intramuscular
Clinical Significance
Testosterone levels achieved
Equivalent
Equivalent
No difference
Peak testosterone
Lower peaks
Higher peaks
IM spikes may drive more side effects
Trough testosterone
Higher troughs
Lower troughs
SubQ more stable between injections
Estradiol levels
Lower post-therapy
Higher post-therapy
SubQ may reduce need for AI
Hematocrit elevation
Lower
Higher
SubQ may reduce polycythemia risk
Pain/discomfort
Less
More
SubQ uses smaller needles, shallower depth
Self-administration ease
Easier
Harder (some sites)
SubQ abdomen is accessible; IM glutes require twisting
Testosterone injection methods comparison
Why the Difference in Estradiol and Hematocrit?
The mechanism appears to be pharmacokinetic. Intramuscular injection creates a rapid absorption curve with testosterone levels spiking within 24-48 hours, often reaching supraphysiological peaks above 1,500 ng/dL on standard doses. One study found serum estradiol increased 1.7-fold within 24 hours of IM injection, driven by the testosterone spike overwhelming the aromatase enzyme system.
Subcutaneous injection creates a flatter absorption curve because adipose tissue has a less dense capillary network than muscle, so testosterone absorbs more gradually. A 52-week study of 150 hypogonadal men using weekly subcutaneous testosterone enanthate found that 92.7% achieved target testosterone levels with “small peak and trough fluctuations”.
I prefer subQ, but even that increased my hematocrit too much so I switched back to a compounded cream from MedQuest which works amazingly well but is more expensive than injectable testosterone.
I did subQ with oil based solutions using 27G insulin needles. I liked it more than intramuscular injections. I never needed to warm the oil although that is a good idea.
Currently I am using oral T from Kyzatrex that you take twice a day. I find that even better although it is more expensive. It is especially good at raising free testosterone.
Sub Q shots are maybe easier for a week before they start to hurt more from repeated injections. IM is way more comfortable with an insulin needle. I assume the study is thinking IM injections are done with the really long, unnecessary needles that most doctors ridiculously tell their patients to use. I remember some urologist trying to tell me I was doing it incorrectly by using insulin needles even though my testosterone level was borderline supra physiological as I was sitting in his office. I tried my best not to roll my eyes.
I tried daily sub Q injections years ago and had a lower testosterone level than when I do daily IM shots. It could have been a coincidence or I could have been injecting too shallow. I’ve been nervous to go back to sub Q ever since.
I do intramuscular its my only frame of referene and highly practical since I use 4 ml for my large injection every 12 weeks or so. It’s the only form available here at least in my case with testosterone prescribed for countering radiation-induced damage that shut down my own production.
Same here. I use 27g x 5/8” insulin needles for IM gluteal and 27g x 1/2” for IM deltoids. Pretty sure the 5/8” needle is the longest available for insulin syringes. I inject daily. No need to heat the oil. It draws up a little slow but since I inject daily it’s a small amount. It’s the first thing I do when I wake up. Well, second thing. I usually go to the bathroom first. It’s no big deal. Takes me less than two minutes from start to finish. The chart in OPs post says subq injections provide lower peaks and higher troughs. Daily IM injection also provide this. More so than less frequent subq injections.
Anything sub 30g gives me nightmares in the middle of the day LOL. If I ever decide on shots for T (doing enclomiphene 12.5mg daily for now) I’ll just do 30g and warm it up before I draw as per @jeanbaptiste and do 1/2" IM on deltoids. I did that exactly for glutathione injections for a while and it was ok, nearly painless.
Have you had a good look at a 27g? It’s tiny. I use 31g for peptides. Not much difference. Some people still use 31g for oil based but it’s very slow to draw up. I personally would rather not risk degrading my testosterone by reheating over and over. Not to mention the waste of time it takes to heat it up especially since I do daily injections. I’m not exaggerating when I say the whole process is less than two minutes each morning. If I had to warm up water and wait for the vial to get warm before I can even start drawing it up, that just seems like such an unnecessary “event”.
LOL. I seem to have plenty now that I’m doing enclomiphene, my balls seem to have doubled in size since I started Enclomiphene LOL. Haven’t measured T yet but will in a month or so.
Why would you be scared of Enclomiphene (real question btw)? I thought T injections might have more side effects, i.e. shutting down the natural T making system.
There is a very real risk of irreversible retinal damage and other vision problems like floaters with long term use of enclomiphene. I think it’s around 10% of enclomiphene users will experience some sort of visual or eye related side effects. If you stop enclomiphene immediately when vision problems occur I think it’s usually reversible. If you continue to use enclomiphene despite symptoms the issue will often become permanent. It could even eventually lead to blindness. It’s in the data and I’ve definitely read multiple anecdotal incidents of this happening on others forums.
I’m not particularly concerned about testosterone shutting down the hpt axis. I’m done having kids. But I do take a low dose of hcg to stimulate the testicles to produce some testosterone, estrogen and neurosteroids. I also test for dhea and pregnenolone and supplement to keep those in the middle of the reference range. I do extensive lab work about every 3-4 months. ALL of my labs are not just good, they are optimal. And I feel great!
Will need to see clinical data on rate of visual disturbances, overall inicidence of side effects, for either enclomiphene or clomiphene. From the data I’ve seen, it’s about 1-2% for visual disturbances, not 10% for clomiphene. It is expected to be lower for enclomiphene.
