How Much Insulin Do You Need?

If you have type 2 diabetes and your healthcare provider thinks it might be a good time to start insulin therapy, you'll likely have two questions: How often do you need to take it, and how much insulin will you need?

A lot depends on your specific situation. The hallmark symptom of type 2 diabetes is insulin resistance, in which the body loses its ability to use the hormone properly. According to the Centers for Disease Control and Prevention (CDC), the insulin-producing cells of the pancreas respond to insulin resistance by churning out even more of the hormone early in the disease. Over time, though, insulin production declines.

Taking insulin can help you overcome the body's insulin resistance, though many factors can affect your dosage. The most important issue is not necessarily how much you need to take but the timing of when you'll need to take it.

One Shot a Day or More?

According to the American Diabetes Association (ADA), most people with type 2 diabetes who take insulin need one injection daily, with or without oral medications. Sometimes oral drugs stop working, and two or more daily injections become necessary. Insulin shots may not be how you picture them. You can use pen-like injectors that have short, thin needles and allow you to dial the amount of insulin you require rather than drawing it up from a vial using a syringe.

If your blood sugar tends to spike after meals despite using medication and watching what you eat, you may have to take a dose of rapid-acting insulin before every meal. A 2018 study in Diabetic Medicine found that taking rapid‐acting insulin 15 to 20 minutes before a meal significantly helps keep blood sugar under control after eating. However, not all healthcare providers support this practice.

"There's controversy over how much better you can really do with additional shots," said John Buse, MD, PhD, director of the Diabetes Care Center at the University of North Carolina School of Medicine in Chapel Hill. "I don't see much improvement in overall glucose control in many patients with the rapid-acting insulin taken at meals. And it does promote weight gain and low blood sugar. Is the burden worth the benefit?"

Either way, a once-a-day long-acting formulation is usually the best way to start, according to Dr. Buse. A standard initial dose might be 10 units. The dosage is then increased until blood sugar levels are lowered into the normal range.

"If a person still has substantial insulin secretion left in their pancreas, one shot a day is probably more than enough to top it off," said Robert Rizza, MD, professor of medicine and executive dean of research at the Mayo Clinic in Rochester, Minnesota. "But if you're really running out of insulin and can't store it between meals, then you may need to take both the long- and short-acting injections."

Taking Insulin With Meals

If you take insulin at meals, it is essential to match food intake with insulin while also accounting for physical activity. According to the ADA, exercise naturally lowers blood sugar, so if you're working out, you may need to consider that.

"Some people recommend matching insulin to carbohydrate counts," said Dr. Buse. "Others suggest eating a set serving of carbohydrates at each meal for a particular dose of insulin."

It Can Be a Vicious Cycle

Nevertheless, an individual may eat well, work out, and routinely take their medicine yet still require more insulin over time due to the progressive nature of the disease, according to the ADA. Adjustments can come through higher doses, increased frequency of injections, or both.

Some people, particularly those carrying excess weight, can reduce their reliance on medications, even discontinuing insulin injections altogether. A 2020 study in the Lancet Diabetes & Endocrinology found that 61% of participants could get off medication when improving their eating and exercise habits led to necessary weight loss.

Additional factors can also affect your blood sugar levels, including stress, illness, sleep, and certain medications, according to a 2018 article in Clinical Diabetes. Checking your blood sugar levels consistently and tracking your trends over time can help you better understand your blood sugar patterns. This information can also help you and your healthcare provider decide on your insulin needs.

"There are multiple ways to get to the same point," said Dr. Rizza. "The bottom line is to keep blood sugar normal."