Insulin
FDA-approved
Also known as: Human insulin
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Insulin is the hormone the pancreas makes to lower blood sugar. It is a small protein of two chains, 21 and 30 amino acids long, joined by sulfur-sulfur bonds. In medical use since 1922, it is essential for life in type 1 diabetes and is also used in type 2 diabetes.
Approved for blood sugar control in adults and children with diabetes (as human insulin, for example Humulin R). Inhaled insulin is approved for people with diabetes aged 6 and older. The two once-weekly insulins are approved, with diet and exercise, only for adults with type 2 diabetes.
How it works
- It binds the insulin receptor on cells, which sets off a chain of signals inside the cell.
- It lowers blood sugar by helping muscle and fat take up glucose, and by stopping the liver from making glucose.
- It slows the breakdown of fat and protein and boosts protein building. The label links its weight gain to these building (anabolic) effects.
- It moves potassium from the blood into cells. This can cause low potassium, and it is why insulin is used in emergencies to bring down dangerously high potassium.
- In a vial, insulin molecules cluster in groups of six around zinc. Most modified insulins (analogues) are designed so these clusters break apart faster or slower under the skin, which sets how quickly they act.
Evidence
Type 1 diabetes
Insulin replacement has never been tested against placebo, and could not be: before insulin, children with type 1 diabetes had a short life expectancy. A trial followed 1,441 people for about 6.5 years. Among those with no eye disease at the start, intensive insulin treatment cut new diabetic eye disease by 76% compared with conventional treatment. Severe low blood sugar was two to three times more common.
Type 2 diabetes
A 10-year trial enrolled 3,867 people newly diagnosed with type 2 diabetes. Intensive treatment with insulin or a sulfonylurea cut small-blood-vessel complications by 25% compared with diet. It did not reduce large-vessel disease, such as heart attack and stroke, during the trial. Over 10 years of follow-up after the trial, heart attacks and deaths became less common in the group first given insulin or a sulfonylurea.
Heart events with long-acting insulin
A trial enrolled 12,537 people with heart risk factors plus type 2 diabetes or early blood-sugar problems. Over about six years, long-acting insulin glargine did not change rates of heart attack, stroke or cardiovascular death. Cancer rates were also unchanged.
Caveats
- Low blood sugar is the main danger. Severe episodes can lead to coma, and low blood sugar slows concentration and reaction time, for example while driving. People with long-standing diabetes may not feel the usual warning signs.
- It can lower blood potassium, which can be life-threatening.
- Weight gain is common.
- Repeated injections into the same spot can thicken or thin the skin there, and insulin injected into that skin may work unpredictably.
- Needles and syringes must never be shared.
- Combined with diabetes pills called thiazolidinediones, it can cause fluid retention and heart failure.
- Inhaled insulin can tighten the airways, so it is not for people with asthma, COPD or other chronic lung disease.
- Bodybuilders who injected insulin to gain muscle have ended up in a coma from severe low blood sugar. No controlled study in healthy people has shown a muscle-building benefit.
References
This page is for education only. It is not medical advice. Decisions about any treatment belong with a physician who knows your history.