A person cannot take insulin as a pill or oral medication. The enzymes in the stomach would break down the insulin before it reaches the bloodstream.
People use insulin injections to treat and manage diabetes alongside dietary and lifestyle changes, and oral medications.
For people who require insulin injections, different types of insulin are available. In this article, we explain how to follow the doctor's instructions on how and where to inject insulin.
Common injection sites
Image credit: Stephen Kelly, 2019
A person needs to inject insulin into the layer of fat directly under the skin, known as subcutaneous tissue, with a small needle or a device that looks like a pen.
Several different sites can support an insulin injection.
The abdomen is a common site for insulin injections that many people with diabetes choose. It is easy to access and often less painful than other sites due to protection by fat, greater surface area, and less muscle.
To give an injection into the abdomen, pinch a section of fatty abdominal tissue, with fingers either side.
The site should be between the waist and the hipbones about 2 inches away from the belly button.
Avoid injecting near any scar tissue on the abdomen.
The upper arm is another possible site for insulin injection.
Place the needle into the tricep area at the back of the arm, about halfway between the elbow and the shoulder.
Difficult self-administration is the main disadvantage of this site. Getting enough of a pinch to administer the insulin can be tricky. A person might need assistance for an injection into the upper arm. They might also experience greater comfort while injecting into the non-dominant arm.
This means injecting into the left arm of a right-handed person or the right arm of a left-handed person.
The thigh is a simple area for self-injection.
When choosing the thigh as an injection site, insert the needle into the front of the thigh, halfway between the knee and the hip. It should be slightly off center towards the outside of the leg.
The injection should take place around 4 inches, or about the width of a hand, above the knee and the same distance from the top of the leg. Avoid the inner thigh due to the denser network of blood vessels in that area.
Inject the medicine into a pinch of at least 1–2 inches of skin.
Though easy to access, regular injections in the thigh can sometimes cause discomfort when walking or running afterward.
Lower back, hips, or buttocks
The final site for administering an insulin injection is the lower back or hip.
To administer an injection here, draw an imaginary line across the top of the buttocks between the hips.
Place the needle above this line but below the waist, about halfway between the spine and the side.
As with the upper arm, this site is very difficult to use for self-injection and may require another person for administration. When injecting into the buttocks, avoid the lower part.
People with diabetes often inject insulin into the abdomen.
The body absorbs insulin at different speeds from each of the sites. This information can be useful when planning insulin injections:
- Abdomen: Insulin enters the bloodstream most quickly after an abdominal injection.
- Upper arms: The body absorbs insulin with moderate speed but slower than an injection in the abdomen.
- Lower back and thighs: Insulin enters the bloodstream most slowly from these sites.
- Administer rapid-acting insulin into the abdomen right after a meal for the fastest results.
Inject long-acting and intermediate-acting insulin into the other sites, as rapid absorption would reduce the effectiveness of these types. Insulin works more efficiently over the entire time it needs to because of the slower absorption rate.
Exercise can increase the absorption rate of insulin. If planning a workout or physical activity, account for these when planning injections.
For example, a baseball pitcher should avoid injecting into their throwing arm. The physical activity can affect the absorption of insulin into the body.
Wait to for at least 45 minutes after the injection to exercise a part of the body that is near the injection site.
Rotating injection sites
Avoid injecting into the same site over and over. This can irritate the skin and underlying fatty tissue.
If this happens, it may increase discomfort and cause other complications. Puncturing the same point every time can lead to hard lumps or fatty deposits developing. This can be uncomfortable and even reduce the body's effectiveness in absorbing the medication.
When rotating injections, move around within the area to ensure that the injection does not always take place in exactly the same spot.
For example, when taking a night time dose of long-acting insulin, a person might always feel more comfortable injecting it into the thigh. However, they should switch between the right and left thigh each night.
If a person always administers a morning dose of rapid-acting insulin into their abdomen, they should alternate between different areas of the abdomen to avoid repeated injections into the same site.
Monitoring blood sugar levels
Ask the doctor any questions about insulin injection, site selection and rotation, and other injection techniques.
In addition, people with diabetes should monitor their blood sugar routinely, as the doctor will advise.
It is important to keep track of blood sugar levels in a diary or notebook for sharing with the doctor. Share any unusual values so that the doctor can adjust insulin dosage and delivery as is necessary.
A person can administer insulin injections into the abdomen, upper arm, thigh, lower back, hips, or buttocks.
Take into account comfort, as injections into some sites can cause pain. Be sure to inject into a pinch of tissue and consider the different methods for injection at each site.
Each site delivers insulin to the bloodstream at different speeds, so consider these depending on the time of day and how fast the body needs insulin.
Avoid repeatedly administering injections to the same spot. Speak to a doctor for advice on switching sites and self-administering.
Are there any alternatives to injection? I have a phobia of needles.
There are some alternatives to injection in the form of an inhaled powder or nasal spray form of insulin. This fairly new approach has shown good glycemic control for persons with diabetes.
Research continues on the safety and effectiveness of these routes of administration. Talk to your doctor to determine if this might be an option for you.Deborah Weatherspoon, PhD, RN, CRNA Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.