Insulin Side Effects

Insulin Side Effects

If you have recently been prescribed insulin, or have switched to a new type of insulin, you may be concerned about the side effects.

You might also be experiencing side effects and not know where they are coming from.

Similarly, you may be looking for information for a friend or family member.

What are the side effects of insulin?

Insulin side effects amongst diabetics are rare, but when they do occur, allergic reactions can be severe and can pose a significant risk to health.

What do I do if I have an adverse reaction to my insulin?

If you experience mild allergic reactions such as swelling, itching or redness around the injection site, experts advise diabetics to consult their GPs. Similarly, sustained nausea and vomiting are signs of insulin allergy.

How do I know if my insulin is working?

When taking insulin, diabetics are advised by experts to regularly check blood glucose levels using testing kits.

If blood glucose tests show fluctuating or above-average blood sugar levels, diabetes is not being properly controlled and insulin is not working.


Insulin is the oldest medication for diabetes and is usually well tolerated by most people. There are various side effects that occur from insulin. Hypoglycemia is the most common, but not the only one. The side effects mentioned in this video are those that are included in patient information leaflets for a number of different insulin types.

Check your insulin’s patient information leaflet to see which side effects are listed as applicable to the insulin you are taking. If you notice any of the side effects, tell your doctor.

Insulin is injected to reduce blood glucose levels and may lead to hypoglycemia. Hypoglycemia is a low blood glucose level which should be treated with carbohydrate. For more information on this specific area please see our treating hypoglycemia video

Some people may get a local allergy –that is itching, redness or swelling at the site of the injection. This will usually clear up within a few days or weeks.

In rare some cases people may get a more severe allergic reaction, known as a systemic allergy, which can include:

  • A rash across the body
  • Trouble breathing
  • Nausea
  • Rapid heartbeat
  • Sweating
  • Drop in blood pressure

Tell your doctor immediately if you have these symptoms.

Lipodystrophy is a relatively rare side effect that causes thickening or pitting of the skin.
It can be described as an abnormality in the way fat is distributed. If you notice bulges or any caving in of the skin, speak to your doctor.

Oedema is known as a swelling of the arms or ankles as a result of fluid retention. Oedema may result from starting or a change to insulin therapy.

And finally, some types of insulin list eyesight problems as a rarer side effect.

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Avoiding infection when taking insulin

When taking insulin, try to avoid infection by using disposable needles and syringes, and sterilising any reusable equipment.

Do some drugs interact with insulin?

Some drugs are known to interact with insulin, and diabetics should be aware of this list. Your GP or physician should provide detailed information of how any extra drug affects insulin.

Some medications that are known to influence insulin are shown below, but diabetics should consult their GP for further information:

  • ACE inhibitors – Accupril and Lotensin
  • Anabolic steroids – Anadrol-50
  • Appetite suppressants – Tenuate
  • Aspirin
  • Beta-blocking blood pressure medicines – Tenormin and Lopressor
  • Diuretics – Lasix and Dyazide
  • Epinephrine (EpiPen)
  • Estrogens – Premarin
  • Isoniazid (Nydrazid)
  • Major tranquilizers – Mellaril and Thorazine
  • MAO inhibitors (antidepressants Nardil and Parnate)
  • Niacin (Nicobid)
  • Octreotide (Sandostatin)
  • Oral contraceptives
  • Oral drugs for diabetes – Diabinese and Orinase
  • Phenytoin (Dilantin)
  • Steroid medications – prednisone
  • Sulfa antibiotics – Bactrim and Septra
  • Thyroid medications – Synthroid

If you cannot find the answers that you need here, please ask a question in the Diabetes Forum

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