[dano]

You probably should elaborate just a little on the insulin that you are injecting. I will assume that you are injecting a long-lasting insulin such as Levemir and not a fast-acting insulin such as NovoLog, which would probably kill a horse in that dosage.

Have you, in the past, had problems with upper GI?
Where is your injection site when this occurs?
At which meal does this occur?

Also: Please revise your post in the Introduction Section, since we don't know if you are T1 or T2.