Diabetes is a serious and complex condition in which your blood glucose, or blood sugar, levels are too high. Over time, high blood sugar levels can affect the entire body and lead to various complications.

In diabetes, your body either cannot make insulin (type 1 diabetes) or the insulin that it does make is not enough and cannot work properly (type 2 diabetes).

What is Insulin?

Insulin is a hormone that acts as a “key” to open your cells, to allow the glucose to enter and allow you to use the glucose for energy. This also maintains blood sugar levels in the body in the normal range (under 140mg/dL).

Many people with diabetes need to take insulin to keep their blood glucose in a good range. Starting insulin may be a frightening and difficult decision to make for some patients, especially for the first time. But with proper education and customized regimen, almost all people can learn how to take insulin and manage insulin at home.

Read more: What is prediabetes?

  1. Where should insulin be injected?
  2. Types of insulin delivery devices
  3. How to inject insulin with a syringe?
  4. How to inject insulin with an insulin pen?
  5. Insulin care and storage
  6. Insulin injection and sites
  7. Disposal and reuse of insulin needles
  8. Other things to keep in mind when taking insulin injections
Doctors for What is insulin and how to administer it

Insulin cannot be taken orally, as a pill or in the form of a liquid, because the stomach enzymes that digest food would destroy it before it reaches the bloodstream. Instead, it is delivered with a syringe or pen into the layer of fat below the skin known as "subcutaneous" tissue.

The layer of fat on the stomach (staying four fingers or two inches away from the belly button), hips, sides of the thighs, and backs of the arms are common sites for injecting insulin. From there, the insulin is absorbed into the bloodstream which then carries it to cells throughout the body.

There are a number of devices that can be used to deliver insulin, including syringes, insulin pens, and insulin pumps. Each device has its own advantages and drawbacks. Ask your healthcare provider for advice on which device (pen or syringe) best suits you. The commonly used devices are:

Insulin syringe

The syringe has been in use since insulin was discovered and it is still widely used, but nowadays insulin pens and pumps are more popular.

Syringes are used with vials (a glass bottle which contains insulin). They are relatively small, disposable, and have fine needles.

The syringes come in different sizes and hold small or large doses.

It is important to inject the right insulin strength with the right insulin syringe; for example, 40IU syringe for a 40IU vial and 100IU syringe for a 100IU vial. IU stands for international unit.

Insulin pens

An insulin pen looks like a large fountain pen. There are two basic types: disposable and reusable. Disposable pens come filled with insulin. When a pen is empty, expired, or has been open for a month, it is simply discarded. In a reusable pen, you can refill the cartridge.

Insulin pen needles are thin and come in a variety of lengths (available in 4, 5, 6, and 8 mm sizes).

Follow these steps to inject insulin using a syringe:

  • Wash your hands.
  • Roll the bottle in-between your palms 10-15 times if you are using cloudy insulin (insulin NPH or intermediate/slow-acting insulin) until the insulin is mixed.
  • Wipe the top of the bottle with an alcohol swab.
  • Take the cap off the syringe, and pull the plunger of the injection down to the required units.
  • Put the bottle on the table, and put the needle into the bottle. Push the plunger down to push air into the bottle.
  • Turn the bottle upside down.
  • Pull the plunger up to the required units.
  • Check for air bubbles. If you see air bubbles, then push the insulin back into the bottle and pull again.
  • Cleanse the skin (injection site) with soap and water or an alcohol wipe.
  • Hold the needle like a pencil.
  • Pinch up the skin.
  • Push the needle straight (at a 90-degree angle) into the skin. Push the plunger down.
  • Wait for 10 seconds.
  • Let go of the pinch and pull the needle out.

Follow these steps if you are using an insulin pen:

  • Remove the cap or cover of the pen (if you are using cloudy insulin, gently roll the pen in-between your palms 10-15 times).
  • Get the needle ready:
    • Remove the paper cover from the outer needle cap    
    • Screw the needle on to the insulin pen
    • Remove the outer needle cap    
    • Remove the inner needle cover to expose the needle
  • Get the pen ready:
    • Prime the pen and clear air from the needle. 
    • Turn the dose selector knob and dial two units of insulin.   
    • Press the dose knob completely and discard two units of insulin in the air.
      Note: Check for an insulin drop at the tip of the needle. Repeat this step if a droplet does not appear. Doing this will remove any air-gaps or bubbles and also ensure a smooth flow of insulin from the pen.
  • Dial in your insulin dose as prescribed: Turn the dose knob to "dial-in" your insulin dose. Double-check the dose window, to ensure that you have selected the correct dosage.
  • Choose an injection site:
    • The abdomen is the most preferred place for delivering many types of insulin. Here's how to pick the right spot if you are injecting insulin into your stomach: pick a spot in-between the last rib and the pubic line, avoiding four inches surrounding the navel.
    • The sides of the thighs and back of upper arms may also be used.
  • Inject insulin:
    • Curl your fingers around the upper end of the pen to hold it firmly.
    • Gently pinch up the skin with your free hand. (This step is not required if you are using a nano-sized needle of 4mm.)
    • Insert the needle at a 90-degree angle for adults and at a 45-degree angle for thin people and children. 
    • Use your thumb to press down on the dose knob until it stops (until the dose window is back at zero). Leave the needle in place for 10-15 seconds to prevent insulin from leaking out of the injection spot.
    • Release the pinch.
      Note: Pull the needle straight out of the skin. It is normal to sometimes see a small drop of blood or bruise. You may lightly pat the site with a tissue or cotton ball, but do not massage the area.

These are some things you need to remember about the proper storage and care of your insulin vials, cartridges and devices:

  • Unopened insulin vials or cartridges should be stored in the refrigerator, between 2ºC and 8ºC. NEVER store insulin in the freezer (temperatures below 0ºC destroy insulin).
  • Opened insulin vials or cartridges can be safely stored at room temperature for up to one month, but below 30ºC (as above 30ºC, insulin’s effectiveness begins to decrease).
  • Protect insulin from exposure to direct sunlight, extreme temperatures (too hot or too cold) and excessive physical trauma (for example, vigorous shaking).
  • Do not use insulin that
    • Is discoloured
    • Is frozen
    • Has been exposed to very high temperatures
    • Has lumps or flakes
    • Has expired
    • Has been open for longer than one month
  • For better comfort and insulin efficiency, take insulin out of the refrigerator at least one hour before your injection; cold insulin may sting and slows insulin absorption rates.

Taking care of injection sites is always important. But it assumes even greater importance when you need to take injections daily or multiple times daily. The following are some things you should keep in mind:

  • Never inject insulin into your muscles, stretch marks or roots of hair.
  • Avoid rubbing the area or exercising the injection site after injection.
  • Injecting insulin through your clothes is not advised.
  • It is not recommended to use soap-based detergents or alcohol swabs at home for cleaning the injection site, but if you do so, make sure skin is dry before injecting (otherwise it will hurt more).
  • Talk to your diabetes care team about injection site selection. Abdomen, thighs or upper arms have more fat and fewer nerve endings—this makes them preferable sites for injection as you feel less pain and discomfort in these areas.
  • Don’t change your injection sites (abdomen, thigh or arms) daily or even on alternate days as it may cause blood sugar levels to go up and down—this is because absorption rates are different at different sites. Preferably use the same site for one or two weeks. But each time you inject, pick a different spot or rotate within that particular site because repeatedly injecting in the same spot can cause discomfort, hardening of the skin or may affect the absorption rate.

Syringes or pen needles are disposable and should ideally be used once. Use a new pen needle before each injection, and never leave the pen needle attached between injections.

Reusing insulin pen needles may cause air to get into the insulin cartridge or may leak fluid which can affect the concentration of insulin and lead to inaccurate dosing.

Reusing needles can also cause more painful injections or tiny fragment of the needle may be weakened and break into the skin.

Take the pen needle off right after use and dispose of it properly in a “sharps” collector. Avoid recapping of insulin needle, as it may cause needle-stick injury.

Sharp disposal

Never throw loose syringes or lancets into the trash. Needles need to be discarded right away in a “sharps” collector, or hard plastic or metal container with a screw-on or tightly secured lid (for example, an empty pill container or detergent jug). Whenever the container is full, seal the lid securely and dispose of properly. Do not put the container into a recycle bin as syringes or needles are not recyclable.

While using insulin of different strength, it is essential that the correct and matched unit syringes are used otherwise you may over- or under-dose.

Do not share your insulin with anyone. Because everybody has different bodies and different requirements. Sharing insulin can be dangerous for anyone.

Dr. Narayanan N K

Dr. Narayanan N K

16 Years of Experience

Dr. Tanmay Bharani

Dr. Tanmay Bharani

15 Years of Experience

Dr. Sunil Kumar Mishra

Dr. Sunil Kumar Mishra

23 Years of Experience

Dr. Parjeet Kaur

Dr. Parjeet Kaur

19 Years of Experience


  1. Davidson M.B. Insulin therapy: a personal approach. Clinical Diabetes, July 2015; 33(3): 123-35. PMID: 26203205.
  2. American Diabetes Association, Arlington, Virginia, US [Internet]. Insulin routines.
  3. American Association of Diabetes Educators [Internet]. Insulin injection know-how.
  4. Michigan Medicine, University of Michigan, US [Internet]. Types of insulin.
Read on app