Insulin: Myths, Types and When It Is Actually Needed

Few treatments carry as much unnecessary dread as insulin. In clinic after clinic, people delay starting it for years, during which glucose stays high and complications develop quietly. The delay is almost always based on beliefs that are not true.

The myths, addressed directly

“Insulin means my diabetes has become serious.” Type 2 diabetes is progressive. The pancreas produces less insulin over time regardless of how well someone follows advice. Needing insulin reflects the natural course of the condition, not a personal failure.

“Once you start insulin you can never stop.” Not necessarily. Insulin is sometimes used temporarily — during infection, surgery, steroid treatment, or at diagnosis when glucose is very high — and stopped afterwards. In type 2 diabetes, significant weight loss can sometimes allow it to be reduced or withdrawn.

“Insulin damages the kidneys.” It is high glucose that damages kidneys. Insulin is one of the few glucose-lowering treatments that is safe at almost any level of kidney function.

“The injections are painful.” Modern pen needles are 4-6 mm and very fine. Most people find a blood glucose finger prick more uncomfortable than the injection.

“Insulin causes blindness.” People often start insulin late, when complications have already developed, and then attribute the complication to the treatment. The sequence is the reverse.

Who needs insulin

• Everyone with type 1 diabetes, from diagnosis, for life. This is not optional; without it the body cannot use glucose at all.
• Type 2 diabetes where tablets and other injectables no longer maintain targets, where HbA1c is very high at diagnosis with symptoms, or where other drugs are contraindicated
• Gestational diabetes not controlled by diet, since insulin does not cross the placenta
• Temporarily during serious illness, major surgery, or high-dose steroid treatment

The main types

• Rapid-acting (lispro, aspart, glulisine): starts in 10-15 minutes, taken with meals to cover the food
• Short-acting regular insulin: starts in about 30 minutes, taken 30 minutes before eating
• Intermediate-acting NPH: covers roughly half a day, usually twice daily
• Long-acting analogues (glargine, detemir, degludec): a flat background level for 24 hours or more, usually once daily, with a lower risk of night-time low glucose
• Premixed: a fixed combination, convenient but less flexible

A common starting regimen in type 2 diabetes is a single long-acting dose at bedtime alongside existing tablets, with mealtime insulin added later if needed.

Using it safely

• Rotate injection sites. Repeatedly injecting the same spot causes lipohypertrophy, lumps of fatty tissue that absorb insulin unpredictably. This is one of the commonest causes of unexplained glucose swings.
• Inject into the abdomen, outer thigh, upper arm or buttock; abdominal absorption is fastest and most consistent
• Unopened insulin is stored in the refrigerator, not the freezer. The pen in use can stay at room temperature for the period stated on the packaging, usually about 28 days.
• Never share pens or needles, even with a new needle
• Check the insulin looks as it should; discard if clear insulin has become cloudy
• Keep spare insulin and needles when travelling, in hand luggage, never in checked baggage

Hypoglycaemia: the real risk to manage

Symptoms of low glucose include sweating, trembling, hunger, palpitations, anxiety, confusion, difficulty concentrating and, if severe, loss of consciousness.

The rule of 15: take 15 g of fast-acting carbohydrate — three teaspoons of sugar or glucose, half a cup of juice, or glucose tablets — wait 15 minutes, recheck. Repeat if still low, then eat a longer-acting snack.

Chocolate and sweets containing fat work more slowly and are a poor choice for treating a hypo.

People on insulin should carry glucose at all times, wear identification, and ensure family members know how to recognise and treat a low. Be aware that hypoglycaemia awareness can fade over years of diabetes, which needs medical review.

When to contact your doctor

• Repeated low glucose readings, especially at night
• Glucose persistently above target despite dose increases
• Lumps or hardening at injection sites
• Any illness with vomiting, which can require dose adjustment and urgent review
• Before starting or stopping steroids, or before surgery

This article is general health information. Insulin type, dose and timing must be individualised by a doctor. Never adjust or stop insulin on your own.