Insulin: Who Needs It?

Insulin can be a lifesaver if you have diabetes, and it's considered one of modern medicine's true breakthroughs. When it first became available in the 1920s, there was only one kind of insulin, still known as “regular” insulin. Today there are many more options-some of them available just since the 1990s.

Insulin: Who Needs It?

Whether it comes from a vial or from insulin-producing cells in the pancreas, everybody needs insulin, of course-not just people with diabetes. But if your pancreas has pooped out, you need to take over its job yourself. That’s not only a task for people with type 1 diabetes. In fact, 30 to 40 percent of people with type 2 need insulin as well, usually because the beta cells of the pancreas can’t manufacture enough insulin to meet the body’s needs (even with medication) or cells become more insulin resistant.

Normally, the pancreas pumps just the right amount of insulin necessary to help cells take up the glucose in your blood. Though a healthy pancreas constantly makes subtle adjustments, there are two basic insulin patterns you need to mimic artificially whether you have type 1 or type 2:

  • A continuous, low-level baseline of insulin to keep blood-sugar levels stable between meals (this is sometimes referred to as basal insulin).
  • Extra bursts of insulin (known as boluses) when blood sugar rises above this baseline level, especially after a meal.

If you have type 1 diabetes, you’ll typically take doses of different insulins throughout the day to cover all your needs. If you have type 2 diabetes, the number of doses you take (and the type of insulin you use) will vary according to how severe your symptoms of diabetes are.

Choosing the Right Insulin

Insulin has improved in both quality and variety over the years, starting with the way it’s made. Until recently, most insulin was extracted from animals, such as cows and pigs, and purified for use in humans. It worked well for most people, but others had allergic reactions, such as redness, itching, swelling, or pain at the injection site. While still available, animal insulin is being used less and less thanks to the wonders of genetic engineering. Today scientists can insert human DNA with insulin-making instructions into bacteria to make them crank out bona fide human insulin as they reproduce.

What matters most about insulin, however, is how it behaves. Available today are insulins that differ in how fast they start working, when their action peaks, and how long they stay active. Insulins are organized into four categories based on how long their effects last.

Short-acting insulin

Regular insulin is now officially classified as “short-acting.” This means that it starts to work quickly but doesn’t last very long. You can use short-acting insulin to provide a burst of glucose control when you need it, particularly in time for a meal. Regular insulin kicks in after 30 to 60 minutes, peaks in three to four hours, and lasts for a total of 6 to 8 hours.

Rapid-acting insulin

Don’t want to wait a half hour to eat while your injection takes effect? No problem: Today there are three rapid-acting insulins (sometimes considered a subset of short-acting insulins) that have been chemically altered to work even faster. Lispro (Humalog), insulin aspart (Novolog), and insulin glulisine (Apidra) start to lower blood sugar in about 5 to 15 minutes, peak in 60 to 90 minutes, and last three to five hours-a pattern closer to what you’d experience after eating if you had a healthy pancreas. Besides allowing you more freedom to eat when you want, rapid-acting insulin is less likely than regular insulin to cause hypoglycemia because it doesn’t stay in your system after the glucose from your meal is used up.

Long-acting insulin

At the opposite extreme are the long-acting insulins glargine (Lantus) and detemir (Levemir). They last all day and night, offering relatively constant action with no pronounced peak over 24 hours. In other words, they closely mimic the pancreas’s background insulin production by holding insulin levels steady over the long haul, with only one injection a day. People with type 1 diabetes need to supplement this type of insulin with a faster-acting agent at meals. But for type 2 diabetes, a long-acting insulin may be all you need, especially if you can still use oral medication.

Intermediate-acting insulin

The effects of these insulins fall in between short-acting and long-acting insulin. Their peaks tend to be higher than long-acting peaks, so they might be better for you if your insulin needs are greater. The two offerings in this category, NPH (neutral protamine Hagedorn) and lente (Novolin L) both contain additives that slow their release-zinc in the case of lente and a protein called protamine in the case of NPH. Cloudy in appearance because of the additives, these insulins start bringing glucose down after about 2 hours, peak in 6 to 12 hours, and keep working for up to 24 hours. They are designed to give you good half-day insulin coverage and are often combined with short-acting insulin.

Inhaled Insulin

In 2006 the FDA approved Exubera, the first inhaled insulin. In people with type 2 diabetes, this short-acting insulin could be used alone or with other diabetes medications (though not with other short- or rapid-acting insulins); people with type 1 diabetes had to use it with a long-acting insulin. When inhaled into the lungs, the drug was then absorbed into the blood, working faster than injected insulin.

In 2007 Pfizer, the maker of Exubera, stopped producing the drug due to disappointing sales, not due to safety issues, although the drug did increase the risk of lung problems, and some patients found the dosing system tricky and the inhaler bulky. Exubera was also more expensive than injected insulin.

It’s likely that another drug company will market a different inhaled insulin in the future, so stay tuned. But keep in mind that inhaled insulin is not for you if you smoke or recently stopped smoking. You also shouldn’t use it if you have a poorly controlled lung disease such as asthma or chronic obstructive pulmonary disease (COPD), which includes emphysema and chronic bronchitis. And you may have to take a lung function test called spirometry before you start the drug and periodically while you’re on it. As with other insulins, inhaled insulin can lead to low blood sugar or even high blood sugar if you use the wrong dose, are taking medicines that affect insulin, or eat too many carbohydrates.

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