Why Changing Treatments and Switching to a New Long-Acting Insulin Puts You at a Greater Risk of Hypoglycemia

There are many reasons why a person with type 1 diabetes might have to change treatment or long-acting insulin. These reasons may include seeking an improvement in blood sugar management, wanting to reduce the risk of nighttime hypoglycemia, when experiencing a change in routine, when transitioning from an insulin pump to injections, etc. Each type of long-acting insulin has its own mode of action, so if you get a prescription for a new type of insulin, it’s important to discuss all of its characteristics with your healthcare team.

Types of insulin and their metabolic effect

Any type of insulin will lower blood sugar, but each one will do so differently. The rapidity and duration can vary from one type of insulin to another.

Insulin glargine (Lantus and Basaglar) is injected once a day and is active for approximately 24 hours. The action of this insulin can sometimes decline before the end of a 24-hour period and therefore not cover a whole day’s insulin needs.

New types of long-acting insulin with a slightly different mode of action are now available, such as a more concentrated insulin glargine (Toujeo) that can last up to 30 hours, and insulin degludec (Tresiba) with a very long duration of up to 42 hours. These two types of insulin are also injected once a day and are covered under the RAMQ as an exceptional medication (which requires that your doctor sign a form). Their longer duration allows for a more consistent coverage of insulin needs over the course of a day. They were also proven to reduce the risk of hypoglycemia and give more flexibility to injection schedules.

It should be noted that the action of insulin degludec (Tresiba) may not become stable until about four days after the first injection. With a longer duration, this insulin stays active in the blood for a longer period than a long-acting insulin with a shorter duration (such as insulin glargine).

Glycemic effect

When taking a newly prescribed type of long-acting insulin, it’s important to be extra careful during the first two to three days. Depending on the duration of action of your old insulin, it might still be active in your blood and act on your blood sugar for a few days. When this happens, the action of the old and new insulin overlaps, which can increase the risk of hypoglycemia.

For this reason, it is important to check your blood sugar more often than usual in the first 48 to 72 hours following a change in dosage or a change of insulin. Make sure you also carry at least 15 g of fast-acting sugar and injectable or nasal glucagon to treat hypoglycemia if needed.

Doctors and endocrinologists can have different strategies regarding a change of long-acting insulin. Reach out to your healthcare team to ask questions and make sure you understand all the related risks and necessary precautions.

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  • Hirsch, I. B., Draznin, B. (2019) Transition of Patients to and from Insulin Degludec: A Clinical Challenge, The Journal of Clinical Endocrinology & Metabolism, DOI: 10.1210/clinem/dgz280

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