I Shoot Up Insulin, "Humulin" About 12 Units In The

I shoot up insulin, "Humulin" about 12 units in the mornng and again in the evening. Out of habit I plunged the needle into the insulin and I pulled the syringe back thinking that it filled then I injected the needle into my abdomen. It was very easy, not like usual and I am now thinking it may have been empty.