The actions of the more modern insulin formulations (lispro, aspart/Fiasp, glulisine, glargine, degludec, and detemir) are not affected much by where on the body they are injected, but older-generation insulins (regular, NPH) can vary considerably depending on where they are injected.
Afrezza inhaler and insulin cartridges
Table 3-3. Insulin Action Profiles
The action of NPH and regular insulin is more rapid in body parts that have greater blood flow. Injecting into the abdomen tends to produce the most rapid absorption, followed by the arms, then the legs, and finally the buttocks. When using these types of older-generation insulins, be consistent about your injection sites. For example, use the abdomen in the morning, thigh at dinner, and buttocks at bedtime. This will minimize the amount of variability in the insulin’s action from day to day.
Injecting any insulin into a body part that will be exercising may accelerate the action of the insulin, particularly when the exercise is performed within an hour of the injection. This is due to enhanced blood flow in the area that is being exercised. For example, injecting insulin into the thigh and then going for a jog may cause the insulin to start working faster, peak earlier, and finish working sooner than usual.
Injecting insulin into muscle will also accelerate its action. Rapid-acting insulin, which normally takes three to four hours to finish working, can do its full work in two hours or less when injected into muscle. This can cause a very rapid blood sugar drop, and it may produce hypoglycemia when given to cover a meal.
Below are a few other tips to help ensure that your insulin works as expected.
Rotate your sites: A condition known as lipodystrophy can affect insulin action.
Repeated injections or infusions into the same small area of skin can cause the fat below the skin to either swell and harden (lipohypertrophy) or wear away (lipoatrophy).
In either case, the absorption of insulin will be altered.
For this reason, it is best to rotate your injection and infusion sites over a large area, and avoid repeating the same spots too often.
If it helps, imagine that you have a monthly calendar printed on each of the body parts where you inject, and inject into the spot that corresponds with that date of the month.
We will cover pump site rotation in greater detail later on.
Store properly: Unopened insulin vials, pens, and cartridges should be stored in a refrigerator (but not frozen).
This should keep your insulin fresh until the expiration date.
Insulin may work fine after the expiration date, but you run the risk of losing some of the insulin’s potency.
The butter compartment on the door might make an ideal home for your insulin.
Once a vial, pen, or cartridge is opened (that is, the rubber stopper is punctured), it may be kept and used at room temperature for up to the length of time recommended by the manufacturer.
This is generally ten days for inhaled insulin, one month for rapid-acting insulin, and six to eight weeks for long-acting insulin.
Room-temperature insulin tends to form fewer bubbles in the syringe and is generally more comfortable to inject.
Again, you may find that insulin works perfectly fine when used beyond a month, but there is always a chance that the insulin may lose some of its potency.
If you choose to use insulin past its expiration date or long after taking it out of the refrigerator, monitor your glucose levels carefully, and switch to fresh insulin at the first signs of elevated blood sugar.
Insulin can spoil easily when exposed to high temperatures.
Your insulin should be kept out of direct sunlight and away from heating devices.
When ordering insulin through the mail, request that it be shipped in a thermally insulated package along with a tag that changes color if the contents are exposed to unsafe temperatures.
When traveling, keep your insulin with you, and do not leave it in a warm vehicle for more than a few minutes.
Do not use insulin that has an unusual appearance.
If it has crystals on the surface or residue at the bottom, is an unusual color, or does not mix uniformly, it should be discarded.
Mix correctly: NPH insulin, or any premixed insulin that contains NPH, needs to be rolled between the palms several times to ensure an even, cloudy mixture.
This applies to vials as well as pens.
NPH may be combined in the same syringe with fast (regular, rapid-acting, or ultra rapid-acting) insulin.
To ensure that your fast insulin is not contaminated during the mixing process, be sure to draw up the insulin in order from fastest to slowest.
In other words, draw the clear (fast) insulin into your syringe before drawing in the cloudy (NPH) insulin.
If a tiny amount of fast-acting insulin gets into the vial of NPH, it usually will not cause any harm.
However, if NPH gets into the vial of fast-acting insulin, it may contaminate the entire vial.
Glargine and detemir should never be mixed with another insulin in the same syringe.
Spare the air: Whether you use syringes, pens, or a pump, eliminating large air bubbles is important. Very small (soda-sized) bubbles are not much of a concern, but larger bubbles can cause your insulin dose to be reduced significantly. Room-temperature insulin is less likely to form bubbles when filling a syringe. If air bubbles appear in your pen or syringe, you should inject them out through the needle (into the air) and then redraw your dose.
Find the right depth: Because insulin is meant to be injected into the fatty layer below the skin, selecting a needle that is the proper length is important.
A needle that goes too deep may accidentally inject into muscle.
Not only does an intramuscular injection tend to sting, but any form of intermediate or long-acting (basal) insulin that is injected into muscle can act much too fast and cause severe hypoglycemia followed by hyperglycemia.
Injections that are too shallow (barely breaking the skin surface) can hurt and may cause insulin to “pocket” under the skin, resulting in incomplete or delayed absorption and high blood sugar.
Remarkably, skin thickness is similar in children and adults as well as in heavy people and lean people, just a couple of millimeters.
It is safe and advisable to use injection needles that are four to six millimeters in length.
If all you have are longer needles, try injecting at an angle in order to avoid accidental injection into muscle.
For those who are extremely lean, it is reasonable to pinch up the skin when inserting the needle and injecting.
And if using a pen, remember to keep the pen needle in for five to ten seconds after pressing the plunger to ensure complete insulin delivery.
If leakage occurs after the injection (insulin appears on the skin surface after removing the needle), consider leaving the needle in the skin longer or using a longer needle and injecting at an angle.
By the way, if the process of inserting the syringe, pen, or infusion set needle into your skin leaves you in a cold sweat, a number of injection aids are available. A list of such devices can be found in