Ask The Expert
Insulin

The term for pulling back slightly on the syringe plunger to check for blood before injection is called aspiration. That technique is used when injecting medication into the muscle (using a longer needle - i.e. 1 to 1 ½ -inches), called an intramuscular injection. The reason for aspirating in that situation is that muscle is more vascular; when medication is injected into muscle, the intention is to have the medication absorb slowly into the muscle and eventually into the blood stream-but not to go directly into the blood stream. So if blood appeared in the syringe before injecting intramuscularly, you would withdraw the needle and reinsert again into a different area.

However, insulin is injected with a much shorter needle (i.e. 5/16 to ½ -inch) into the subcutaneous tissue, which does not contain major blood vessels. To avoid hitting a vein, gently pinch up a two-inch or three-inch area of skin. Hold the syringe like a pencil close to the site, keeping your fingers off the plunger.

• If you are overweight, it is best to use a regular, ½ -inch needle and to insert it straight in, at a 90-degree angle.
• If you are a thin adult or are giving the injection to a small child with little fat, you would use a shorter needle (3/16" or 5/16 ") and would insert it at a 45-degree angle. This will prevent the insulin from being injected into muscle, causing it to be absorbed more quickly.
• Note that if blood appears on the skin after you withdraw the needle, that does not mean you gave an intramuscular injection and/or hit a vein, but rather it is just likely the needle went through a tiny capillary.
• As always, remember to review all this with your diabetes team. Your diabetes educator should supervise and review your injection technique to be sure it is appropriate for your situation.