Insulin

What is it?

According to the NIDDK, insulin is a hormone normally made by the pancreas. According to MedlinePlus, it helps move sugar from the blood to the body's other tissues to be used as energy, and stops the liver from making excess sugar.

Insulin is used as a drug when the body does not make enough. The NIDDK explains that its types vary in speed of onset and duration of action, and a person may need more than one type (MedlinePlus).

Its types as given by the NIDDK: rapid acting and ultra-rapid acting, short acting (regular), intermediate acting, long acting and ultra-long acting, as well as ready-made mixtures. The NIDDK described the ready-made mixture as a combination of the insulin types mentioned that begins to act within a short time and lasts for hours. The NHS page classifies the types into five categories: rapid, short, intermediate, long acting, and biphasic (mixed).

The time differences as the NIDDK gave them approximately: rapid begins after about a quarter of an hour and lasts a few hours, short begins after about half an hour and lasts longer, intermediate begins after hours and lasts about half a day or more, long begins after about two hours with no clear peak and lasts about a day, and ultra-long lasts longer than that. These are general differences, and the doctor chooses the type and its timing.

The names of the types here are limited to what the main NHS page and the NIDDK page mentioned.

Uses

Type 1: "If you have type 1 diabetes you must take insulin because your pancreas does not make it" (NIDDK). The NIDDK adds that most people with it need it daily to control blood sugar and to stay alive.

Type 2: many people need it with oral drugs or instead of them, especially as time passes (NIDDK). MedlinePlus says it is prescribed for people whose blood sugar is not controlled with oral drugs alone. The NHS notes: "If metformin or other diabetes drugs do not help you may need insulin".

Gestational diabetes: if lifestyle changes are not enough the doctor may recommend insulin, and the NIDDK notes that it is "safe during pregnancy".

MedlinePlus notes that insulin alone may not be enough in rare cases to control blood sugar, and the doctor may add other drugs with it (NIDDK, MedlinePlus).

How it is used

According to MedlinePlus it is usually injected under the skin, often several times a day, and some forms may be given into a vein by the medical team. It comes in vials, ready-to-use devices and pen cartridges. In type 1 the NIDDK notes that it is taken several times a day, especially with meals.

Methods of administration according to the NIDDK: (1) Needle and syringe: the amount is drawn from the vial. (2) Pen: resembles a writing pen and has a needle, some are pre-filled and thrown away after use and some have replaceable cartridges, and it says many people find it easier but it is more expensive. There are "connected" pens with memory and data reports that help the patient and doctor. (3) Pump: a small device the patient carries that delivers insulin continuously, some with a tube and needle and some that stick to the skin, and the placement site is changed every few days, and they can be programmed for extra doses at meals.

Less common methods according to the NIDDK and MedlinePlus: inhaled insulin (for adults with type 1 or type 2 only), the high-pressure jet injector instead of a needle, and injection ports. The NIDDK describes the "artificial pancreas", a system that combines a continuous glucose monitor, software on the phone and a pump that adjusts insulin automatically.

Injection sites according to the NIDDK: the abdomen (absorbs fastest), thigh, buttocks, and upper arm (slowest). According to MedlinePlus: change the injection site so that each injection is separated from the next by a distance of at least about half an inch within the same general area before moving to another area, and do not inject into muscle, a scar or a mole.

Why rotate? The NIDDK warns that injecting repeatedly into the same place may cause the tissue to harden, making it difficult to inject there later. The NHS notes that repeated injection at the same site is among the causes of low blood sugar.

Timing and food: MedlinePlus stresses keeping to the times, amount and type of meals, because skipping or delaying a meal or changing the food may cause problems with blood sugar control. "Do not use more or less insulin, or more often, than your doctor prescribed", and do not change one type for another without their approval.

Storage according to MedlinePlus: unopened is kept in the refrigerator without freezing; opened vials in the refrigerator or a cool dark place away from heat; and opened pens and devices at room temperature. Do not share needles, syringes or pens with anyone. Supplies are disposed of through medicine collection programmes and are not thrown in the toilet.

Side effects

Non-serious effects according to MedlinePlus: redness, swelling or itching at the injection site, change in skin thickness (thickening or dimpling), weight gain, and constipation. MedlinePlus points to the subject of weight gain with insulin, and the NIDDK lists weight gain among the common effects of diabetes drugs.

The most serious and most common in use: low blood sugar when insulin is not balanced with food and activity (NIDDK). Its detail is in the warnings section below.

Warnings and precautions

Early signs of low blood sugar according to the NHS and NIDDK: hunger, dizziness, sweating, shakiness, numbness or tingling in the lips, palpitations, tiredness, blurred vision, confusion and headache. During sleep there may be shouting, nightmares or heavy sweating.

Severe low blood sugar: loss of consciousness or seizures, which the NIDDK describes as dangerous and needing immediate treatment and may lead to fainting, coma or death. MedlinePlus notes that excess insulin, too little food or more exercise are among its causes, and advises calling poison control or emergency services in severe cases.

Causes of low blood sugar according to the NHS and NIDDK: taking too much insulin, injecting repeatedly in the same place, skipping meals or too few carbohydrates, intense physical activity (its effect lasts up to about a day), alcohol without food, and illness that affects appetite. This is why MedlinePlus advises checking blood sugar before driving or operating machinery.

What the pages say for mild to moderate low blood sugar: take a quantity of fast-absorbing carbohydrate immediately (a glucose tablet, juice, sugar or a sugary drink according to the NIDDK and NHS), then recheck blood sugar after about a quarter of an hour (NIDDK) or after 10 to 15 minutes (NHS), and repeat if it remains low. After improvement the NIDDK advises a snack if the next meal is more than an hour away, and the NHS advises slowly absorbed food. The exact amount and the emergency plan are decided by your medical team.

Severe low blood sugar with loss of consciousness: according to the NHS, do not give food or drink to an unconscious person, put them in the recovery position, give a glucagon injection immediately if available and you know how to use it, and call an ambulance if it is not available or does not improve quickly or if they have drunk alcohol. According to the NIDDK glucagon is available as an injection or nasal spray, relatives and colleagues are trained in it, emergency services are called after it is given, and carrying a medical ID card or bracelet is advised.

The NIDDK warned of repeated low blood sugar: it may lead to high blood sugar if the patient avoids the drug out of fear, or to "hypoglycaemia unawareness" so that symptoms do not appear until blood sugar falls dangerously.

Serious effects that call for immediate care according to MedlinePlus: rash and itching over the whole body, difficulty breathing or wheezing, dizziness and blurred vision, fast or irregular palpitations, muscle cramps, rapid weight gain, and swelling of the limbs.

Tell the doctor before starting, according to MedlinePlus, about: an allergy to insulin or anything else, medicines and supplements you use, previous nerve damage from diabetes, heart failure, glandular or organ diseases, pregnancy, an upcoming operation, and alcohol drinking habits.

Monitoring

According to the NIDDK, testing blood sugar at home helps avoid dangerous highs or lows and shows the effect of foods. It is done with a device that measures a drop of blood from the finger, or with a continuous monitor with a sensor under the skin that displays changes and sends alerts, and it is part of the artificial pancreas.

The CDC notes that people with type 1, or type 2 who take insulin, or who have frequent lows, may need to test more often, including before and after physical activity. It notes that taking too much insulin is one cause of low blood sugar, and that not taking enough may cause it to rise.

The glycated haemoglobin (A1C) test reflects average blood sugar over about three months and is done by the medical team, and the NIDDK notes that the target for most people with diabetes is below 7% though individual targets differ; your personal target is set by your doctor.

According to MedlinePlus: keep your medical appointments and blood sugar tests, update your medicine list, and do not change the type of insulin without your doctor.

Special situations

Pregnancy: the NIDDK says insulin is safe during pregnancy in gestational diabetes. MedlinePlus asks you to tell the doctor about pregnancy before starting. This page does not cover pregnancy and breastfeeding in detail.

Children, older people and kidneys: this page's sources do not address these groups specifically, so refer to the doctor.

Acute illness: the NHS advises people with type 2 diabetes on diabetes drugs to tell the medical team in case of vomiting, diarrhoea or high fever, and the doctor may temporarily stop treatment; the decision is the doctor's.

Common situations

According to MedlinePlus: if you forget a dose, consult the doctor to know what to do, and write down their instructions to refer back to. Do not make up for it with a personal decision.

For safe disposal: do not throw needles and pens in the toilet, and use medicine collection programmes (MedlinePlus). In an emergency or overdose, call poison control or local emergency services.

Common questions