Diabetes Forecast

Can I Change Insulins?

In 2005, I was put on insulin glargine (Lantus), switching from NPH and regular insulins. I’ve had diabetes for 20-plus years. The cost of the insulin keeps going up and, when I reach the Medicare Part D“doughnut hole,” is almost $300 a month. My doctor is reluctant to put me back on NPH and regular or try70/30. Would it be difficult to switch? Name Withheld

Craig Williams, PharmD, responds:

Insulin remains our most effective therapy for lowering blood glucose. But using it effectively and safely requires ongoing attention and adjustments from both providers and patients.

What to Know

First, key differences exist in the time over which various insulins will act, and so we cannot just convert unit for unit between different products. Lantus is long-acting and generally effective for about 24 hours after an injection. A combination of two insulin types, 70/30 is 70 percent NPH insulin, which is medium-acting (about 12 to 16 hours), and 30 percent R insulin (Regular), which is short-acting (about four to six hours). Second, the action of insulins differs from person to person because bodies differ in how they absorb the medication. So, general rules about converting might need to be adjusted for each individual. Finally, longer-acting insulins have a lower risk of hypoglycemia (low blood sugar) because the amount of insulin in the blood at any one time tends to be lower compared with similar amounts of shorter-acting preparations. It’s very important to avoid hypoglycemia.

Possible Solutions

When first converting from a long-acting, once-daily insulin such as Lantus to a regimen with NPH, we would lower the total daily dose by about 20 percent to reduce the risk of hypoglycemia until we learned how the new insulin worked in that person. The addition of a short-acting insulin such as Regular should be individualized based on blood sugar readings after meals.


Insulin is an effective, highly individualized therapy; patients and providers should feel comfortable in trying—together— different regimens to find what works best. Long-acting, once-daily insulin has a lower risk of hypoglycemia, but it’s also fair to consider the costs of insulin in figuring out what is best for you.



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