I'm getting ready to take my first official T shot. My gf wants to do it in my deltoid muscle (in the upper arm/where a flu shot would go). I have always heard the deltoid is a bad spot to do them but never heard why. We've been looking online for answers but haven't found anything. It looks like cis males use the deltoid all the time for their T shots.

Is there a certain reason why the deltoid isn't recommended?

The nurse also gave me a bag of 21g needles saying 23g was too small. These things look like spears, lol.

...my gf is an EMT (studying to be a paramedic) and she says she wouldn't be comfortable sticking something that large in me. She says it looks like what they pierced her nipples with, lol.

...anyways, does anyone have a clue why the deltoid muscle isn't recommended for T shots?

I also heard this, my girlfriend said there are more veins in the deltoid muscle, I don't know if it's true. Don't worry about the needles, they just look scary but don't hurt more than a smaller one. 

Anyway, I think this video is helpful those who are self injecting, really old but helpful:

"Anyway, I think this video is helpful those who are self injecting, really old but helpful"

Oh, needles! <passes out on floor>

At exactly 12 noon on December 18th, 2012 I took my first T shot!

I prepared the needle and my gf injected me.

Yes, we used the 21g, in the arse muscle, and it felt like a flea bite, lol.

Some of you guys had me thinking it would hurt, lol. Ya boogers...

I've never actually heard that.
But I've never liked taking my shot in my delt, it's more difficult for me.
Especially when I'm using my left hand to take it, since I'm right handed.
I've always preferred taking my shots in my thighs,
and my doctor said that there's no issue with me just switching between my legs and not taking it in my delt.

Congrats Simon, and sorry Devlyn, good thing you're on the other side 

also a reason against the delt is it is smaller which is worse for absorption.

I use 21g in my thighs.  It might just sound too large, but I've never had a problem.  I know someone who used 23g and he said it hurt less, but it also took like a whole minute to push the T out of the needle because the needle was so narrow.