Blood pour into syringe while injecting

So I pinned just this morning 2 mins before typing this because it literally scared the shit out of me.
I pinned Tren ace 100mg with a 25g 5/8 inch terumo brand.
I don't personally like this syringe I feel the bore is bigger than the 25g 1inch BD brand and it hurts. I pinned my delt as usual, aspirated as usual and it went normal as usual, things were fine, I waited 3 seconds after injecting the full mg until blood started flowing into the syringe I panicked and pulled out and blood flowed like crazy like a long stream of blood down my arm wiped it with alcohol swab and bleeding stopped. iirc I shot this delt 4 days ago. What caused blood to flow in the syringe while the plunger was pushed?

You perhaps passed through a vein while piercing the skin and mid injection pulled the pin back ever so slightly, allowing the tip of the pin to enter the vein

Scar tissue. Happens all the time except this is an extreme example as the blood usually will squirt out upon removing the needle. In this case, there was enough pressure built up when pushing the oil into an area with scar tissue which caused the pressure to build up and the blood to rush right into the syringe.

It's not a big deal but you will want to rotate sites more often. Maybe steer clear of delt injections for a while. Try hitting your lats instead. Much bigger muscle, more place for the oil to go so less pressure build up and no blood squirting out! (Eventually the same thing may happen in your lat, too, so it's important to continue rotating sites.

* forgot to mention that, yes, there was def a vein present in the area as well since capillaries wouldn't produce that much blood.

Like Hollowedzeus said you were near a blood vessel, more specifically an artery, and damaged it moving or removing the needle.

Dont inject into front deltoid as it is much more likely to hit axillary artery, or too low on side deltoids not to hit the deep brachial artery.

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Originally Posted by Mr.BB

Dont inject into front deltoid as it is much more likely to hit axillary artery

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BB do you think he could get to it with that needle?

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Originally Posted by kelkel

BB do you think he could get to it with that needle?

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Small deltoides ? :lol: Joking :) Good catch, did not noticed the needle size. My reading skills are lacking :(

Still definitely an artery. Cant remember the name of the smaller ones that branchs into the delts.

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Originally Posted by Mr.BB

Small deltoides ? :lol: Joking :) Good catch, did not noticed the needle size. My reading skills are lacking :(

Still definitely an artery. Cant remember the name of the smaller ones that branchs into the delts.

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You had me worried for a minute there!

It happens. I pin quads and glutes as a rule but have done delts when I wanted to change up.

It's very probable you pinned the deltoid branch of the thoracoacromial artery which is a branch of the axillary artery. Besides location, another way to have a better idea if it was an artery or vein is by looking at the color of the blood. Blood coming out of a vein is always dark red, even bluish-red since it lacks oxygen. From an artery is more of a normal red. In your case the location is more consistent with an artery. It's nothing to worry about.