Beginning a new prescription of insulin, or a different type of insulin, can make you feel anxious regarding potential side effects.

If you’ve recently just been prescribed insulin, you may not be aware of the possible side effects that can occur, or realise what’s causing them.

Can insulin cause problems?

Insulin side effects are rare, but you may feel slightly shaky and hungry when first taking insulin. These side effects are only temporary and should go away within two weeks.

Hypoglycemia (low blood sugar) is the most common side effect of insulin, which is why frequently checking your blood glucose levels is important to stop them falling too low.

Severe hypoglycemia is a much more serious complication which can lead to a loss of consciousness or neurological problems, with one cause of this being insulin overdose.

Allergic reactions

Allergic reactions to insulin can be severe and pose a significant health risk for diabetics.

It can be common for there to be bruising in certain injection sites, especially if you inject in a specific area often, but regular rotation will allow this skin to heal.

However, if you experience mild allergic reactions such as swelling, itching or redness around the injection site, you should contact your doctor or diabetes team.

Sustained nausea and vomiting are also signs of insulin allergy. If you believe you are having an allergic reaction to your insulin you should inform your prescriber or pharmacist.

How do I know if my insulin is working?

There are a number of reasons why insulin may not be absorbed quickly, which can give the impression it is not working.

Injecting insulin into the abdomen (stomach) will result in faster absorption than compared to injections in the thighs or arms.

Injecting in the same spot continuously, meanwhile, can cause scar tissue to build up, which slows down absorption.

If you inject into areas where there is more fat, you may see insulin absorption slowed down due to there being fewer nerve endings. This can, however, be a more comfortable place to inject.

Blood testing

Diabetics are urged to check blood glucose levels regularly when taking insulin, as this will help you monitor how well the insulin is working.

If you receive fluctuating results, or regularly above-average blood sugar levels, your diabetes is not being properly controlled and your insulin may not be working efficiently.

Avoid reusing needles

Reusing syringes or needles when injecting insulin increases the risk of infection, and you should change them at least once a day.

There are a number of additional situations in which reusing of needles or syringes should be avoided, including:

  • Suffering a parallel illness
  • Living in an unhygienic environment
  • Having open wounds that have not healed
  • A decreased resistance to infection

Do some drugs affect insulin?

Some drugs can interact with insulin, which may affect delivery and the ability of people with diabetes to recognise low blood sugar.

Your doctor or consultant should be able to provide you with detailed information on which drugs can affect insulin, which include:

  • ACE inhibitors – Accupril and Lotensin
  • Anabolic steroids – Anadrol-50
  • Appetite suppressants – Tenuate
  • 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

Certain prescription and over-the-counter drugs may also affect how insulin is delivered, as well as vitamins and herbal products.

You should inform your GP whenever you start or stop using a medicine and investigate beforehand whether it could affect your insulin.