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Insulins

Before you developed diabetes, your body produced a low level of insulin all day and all night. This is called basal or background insulin. When you ate, your body produced extra insulin, or a bolus. The pattern of the bolus depended on how big your meal was and what types of food you ate.

Your Insulin Levels Before You Developed Diabetes

If your blood glucose levels are too high, your pancreas is not producing enough basal insulin, or it’s not producing enough insulin after meals, or both. You can make up for these shortages by supplementing with injected (or inhaled) insulin.

TYPES OF INSULINS

Basal Insulin

A good basal insulin provides a low, steady amount of insulin activity. It also has a long duration. It lasts at least half a day to as long as 24 hours, so you’ll need to take it only once or twice a day.

Two insulins meet these criteria: glargine and detemir. Another insulin used for basal coverage is NPH. NPH does have a peak, but it’s very broad. We discuss the pros and cons of these three insulins on BASAL INSULIN PLANS: THE INSULINS.

Bolus (Mealtime) Insulin

A good bolus insulin starts to work soon after you inject it (a quick onset), so you can take it right before you eat. It also has a sharp peak: a lot of insulin activity during the two to three hours that the glucose from your meal is entering your bloodstream. Then, ideally, the insulin activity will drop off.

The rapid-acting insulins meet these criteria. Regular insulin is also used for meal coverage, but its peak is not as sharp and lasts longer. See Regular vs. Rapid-Acting Insulin.

Action Profiles of Insulins

Action Curves of Insulins

Insulin: Onset, Peak, and Duration

Onset: How soon after injection the insulin begins lowering blood glucose. Also known as lag time.

Peak: When the insulin is lowering your blood glucose levels the most. It’s important to know the onset and peak for your mealtime insulin so you know when to take it.

Duration: The total time the insulin lowers your blood glucose.

MANUFACTURED INSULINS

Years ago, people used animal insulins. Today, we use “human” insulin and the insulin analogs.

Human insulin is made in labs. The genetic code for human insulin is inserted into bacteria or yeast so they produce human insulin. Different additives in human insulin produce different action profiles.

The insulin analogs—aspart, lispro, glulisine, glargine, and detemir—are the newer insulins. They’re like human insulin but with small changes in the chemical structure. These changes produce insulins with different action profiles. Insulin analogs are also made in labs. They require a prescription. Some insurance plans cover the older insulins but not the insulin analogs, which are more expensive.

Insulins Available in the U.S.

* Note the difference between Novolin 70/30 (30% regular) versus NovoLog 70/30 (30% rapid-acting aspart).

Premixed Insulin

Although people talk about premixes as though they contain two insulins, it’s really just one insulin. A binding agent is added to rapid-acting or regular insulin. This makes some of the insulin (75%, 70%, or 50%) intermediate acting. People often refer to this part as “NPH.” You inject a premix before a meal. You get a peak from the rapid-acting or regular portion and then a long trailing off that gives basal coverage.

Cloudy Insulins: Rock ‘n’ Roll

NPH and the premixed insulins are normally cloudy. These insulins settle when they sit around, like orange juice that sits in your refrigerator. You have to gently remix any cloudy insulin every time before you use it. If you don’t, the doses you draw will be different from each other and will give unpredictable results.