If you’re taking basal insulin therapy, your treatment approach will be different from others with type 2 diabetes. Even if you’ve been taking this type of insulin for a long time, it’s good to remind yourself how basal insulin therapy works in your body. Here’s a guide to help you ask your doctor the right questions during your next appointment.

The American Diabetes Association defines basal insulin as “background insulin.” It works in normalizing blood sugar level during periods of sleeping and fasting, like between meals.

Long-acting insulin mimics the action of basal insulin. The body absorbs this insulin slowly, so the effect can last for up to 24 hours, depending on the type of insulin you use.

As you may already know, there are two types of basal insulin: intermediate-acting and long-acting. Both help maintain a normal blood sugar level during fasting.


Intermediate-acting insulin (NPH), such as Novolin and Humulin, starts to take effect two hours after using it. The peak of the insulin is six to eight hours after injection, but the effects can last for 8 to 12 hours. This type of insulin is taken once or twice a day, depending on the recommendation of your endocrinologist.


Long-acting basal insulin, such as Detemir and Glargine, takes effect two hours after the shot. This insulin can stay in the bloodstream for up to 24 hours. It’s usually taken before bedtime. The benefit of long-acting insulin is that is doesn’t peak, so there’s less of a chance of low blood sugar.

A good follow-up question to ask your doctor would be: “Which type of basal insulin is good for my condition and why?”

Basal insulin therapy helps the body mimic its normal insulin pattern within a 24-hour cycle.

Your endocrinologist can recommend a dosage depending on your blood sugar levels during the day. If your blood sugar level is high at fasting and before meals, your endocrinologist will increase the dosage of your basal insulin. This would also mean that basal insulin dosage isn’t a one-size-fits-all treatment plan.

Factors that affect the dosage

Your endocrinologist considers other factors that may affect the dosing of basal insulin. Your activity level, stress, hormonal changes, and overall health all affect your blood sugar level.

For instance, stress can increase glucose release or reduce insulin sensitivity, which means that your body needs more insulin to help sugar get from the blood and into the cells.

Hormonal changes in the body can also affect blood sugar levels. A study published in ILAR Journal noted that the sex hormones estrogen and progesterone can modulate glucose tolerance and insulin sensitivity. These ovarian hormones can affect insulin sensitivity during pregnancy, across the menstrual cycle, and during menopausal transition.

Illness may also increase your blood sugar levels due to infection. Being sick can trigger more physical stress, which can affect blood sugar levels.

Because many factors affect the dosing of basal insulin, it’s important to note that when your endocrinologist changes your basal insulin dose, your bolus doses will also be affected, if you’re on a basal-bolus regimen. This is especially true if you’re already taking basal insulin.

Testing your blood sugar levels throughout the day is crucial to check how any changes in your basal insulin affect your blood sugar level.

Ask your doctor if there’s a need for you to adjust your dosage in times of sickness, as well as during a pregnancy or a menstrual cycle, if applicable.

Basal insulin therapy is good for maintaining normal blood sugar levels for 24 hours. But just like other types of insulin, it has side effects.

The most common side effect of basal insulin therapy is hypoglycemia, or low blood sugar. This may occur during a period of fasting, particularly during sleep. However, the risk of low blood sugar with long-acting insulin is generally lower since it doesn’t peak, but rather has a “flat” action that works all day and night.

Symptoms of low blood sugar include sweating, irritability, anxiety, dizziness, weakness, headache, confusion, and fainting. These can be prevented by changing the dosage of your basal insulin under the direction of your endocrinologist.

Some other possible side effects of long-acting insulin are edema, weight gain, and allergic reactions, particularly on the injection site. Allergic reactions may cause itching and the development of rashes.

If you experience shortness of breath, palpitations, swelling of the face or throat, dizziness, sweating, and confusion, you need to seek medical help immediately. These reactions may lead to severe health problems and can even be deadly.

Knowing how basal insulin works is important before you use it to manage your diabetes. Asking the right questions of your endocrinologist is crucial so that you can understand what this treatment is all about.

Now that you’re armed with more knowledge, you can ask relevant questions the next time you pay your doctor a visit.