IM vs SUBQ HRT Injections & What All That Even Means

A Medical Transition often requires one of two injection methods, so what's the difference?

An important part of transitioning for some are the effects of HRT or Hormone Replacement Therapy. For a Medical Transition a Doctor will prescribe a regular dose of synthetic Testosterone to help the body develop masculine characteristics.

Currently, there are two methods that are covered by insurance and seen as the best ways to introduce Testosterone (T) into the body.

Injections, and Topical Gel.

Putting the gel aside for a moment, let’s talk about the differences in the two injection types: SubQ or Subcutaneous, and IM or Intramuscular


NEEDLE LENGTH is the most obvious difference. For those who are apprehensive about using needles, the SubQ size of 1/2″-5/8″ long ends up being more appealing. The length of each is in response to the bodily system you’re asking to process the Testosterone, and therefore how deep you’ll need to go in.

Another point of sizing to talk about is the GAUGES. T is a thick substance so the needle you use to pull the T out of the bottle, and the needle you use to inject yourself are often different.

A 16-18 Gauge Needle is perfect for getting it from the bottle into the syringe. A SubQ Needle can be as tiny as a 27 Guage, where an IM needle can be no bigger than a 23. (The smaller the number, the smaller the diameter).

Always remember to only use needles once, here’s why.


When groups of tissue join together with a common purpose, the medical world calls them Systems. Most medicines these days are in pill form and are processed through your Digestive System, but there are other methods of delivery into the body. A digestive form of T either can’t be absorbed properly or hasn’t been created yet.

The elimination of testosterone in blood is about 70 minutes, so it is necessary to have a continuous supply of the hormone for masculinization. This is achieved by injecting into a System that slowly releases the Hormone into the bloodstream.

SUBQTHE TRADITIONAL VIEW of adipose tissue as a passive reservoir for energy storage is no longer valid. Adipose tissue is now known to be a very important and active endocrine organ. It is well established that adipocytes (or fat cells) play a vital role in the storage and release of energy throughout the human body. More recently, the endocrine function of adipose tissue has been discovered. 

Testosterone that is injected via SubQ needles is absorbed by the body and into the bloodstream ‘more slowly’ than that of IM injections so the frequency and amount are different.

A study of SubQ vs IM injections was published by The Journal of Clinical Endocrinology & Metabolism, Volume 102, Issue 7 where they tested out the delivery method within 63 FTM patients. “Data from our patients indicate that long-term SC administration of T cypionate to FTM transgender patients is effective, safe, and well accepted”. – READ MORE 

Injections via SubQ are given at an angle into an area high in fat, such as your stomach, buttocks, or thighs (Visual Diagram). Smaller doses of T are given in to this system and injections tend to be about 7-8 days apart.

INTRAMUSCULAR – THE DEPTH of the needle puts the substance into the deep tissue of the muscle. Here it is absorbed more quickly into the bloodstream.

This may seem like it’s the hands down way to do it, and for a long time it has been, but with more research Doctors have found that in the end there is no difference in the way it causes a Transition and its effects on the body.

Larger doses of T can be administered here, and frequency tends to be anywhere from 10-14 days apart. The injection is given at a 90 degree angle, straight into the muscles in areas of the thighs and buttocks.

UNOFFICIAL ADIVCE FROM THE AUTHOR: While I’m not a medical Doctor, I have had the experience of both SubQ and IM (And so have these guys), and I’ve been administering my own shots for 11 years as of 2019.

TL:DR – I prefer SubQ in all the ways.

My first 8 years were IM, I didn’t even know there was another way to do it honestly. After the weekly stabbing of a muscle for prolonged periods of time (even if you rotate) it starts to hurt in a way that it didn’t used to.

With shots done in your lower back / buttocks area, you run a risk of hitting serious nerves including your Sciatic. With shots done in your thighs, you run the risk of not rubbing it in well enough and having a nob of T give you a limp for a few days.

My SubQ shots are done in my stomach. That little donut of fat I’ll never get rid of has a new purpose! – I switch sides of my belly button every week, doing .5cc every Tuesday. I’m not going to lie to you, it’s still an injection and it still kind of hurts, but the needles are half the size and you’re sinking it into cushion instead of stabbing it toward your bone.


Author Ryan Sallans talks about his experience with both SubQ and IM injections.