What gauge/needle length are you using and what is your T protocol (dose of T/injection frequency)?
My reply from an older thread:
Whether injecting sub-q/IM many may also run into issues with leakage of the oily solution/blood post-injection.
When using a fixed LDS insulin syringe 27-31G injection site leakage of the oily solution let alone blood should be minimal--->non-existent if using a proper injection technique.
Pushing hard on the plunger after injecting can cause the rubber stopper to compress causing a suction/vacuum effect (flow back) which can cause leakage of the oily solution.
Never force the plunger after injecting otherwise you will increase the chance of flow back.
Just inject slow and steady (less trauma) to surrounding tissue.
It is normal to sometimes get some blood leakage (minimal) let alone oily solution after injecting especially if you nicked a vessel on the way in or anytime you pierce the skin.
Avoid pressing hard on the plunger after injecting and it will make a big difference in preventing any flow back (oily solution/blood).
I find piercing the skin quick than injecting slow and steady with minimal pressure from start to finish works best.
