'Overbasalization' Common in Type 2 Diabetes Management

Miriam E. Tucker

May 27, 2021

Overuse of basal insulin rather than adding therapies that target mealtime glucose levels is a common problem in primary care management of type 2 diabetes that impedes achievement of optimal glycemic control, new research suggests.

Such 'overbasalization,' defined as a hemoglobin A1c of greater than 8% despite use of more than 0.5 units/kg per day of basal insulin, was identified in about 40% of patients seen in a Florida primary care clinic during 2015-2018. The findings were published in the April 2021 issue of Clinical Diabetes by Kevin Cowart, PharmD, a diabetes care and education specialist at the University of South Florida, Tampa, and colleagues.

The literature suggests that once people with type 2 diabetes start basal insulin, the chance that they'll achieve a given hemoglobin A1c target, i.e., less than 7%, diminishes significantly if that goal isn't achieved within the first year of starting insulin, Cowart said in an interview.

"Our analysis suggests that overbasalization plays a role in patients with type 2 diabetes on basal insulin not achieving optimal glycemic control. Basal insulin is not designed to address postprandial hyperglycemia. I think there's a clear need to address hesitancy in therapeutic progression beyond basal insulin. A lot of factors underlie the delays, with therapeutic inertia being one of them. It's complex," he said.

Overbasalization Seen in Large Proportion of Patients

The study comprised 655 adults diagnosed with type 2 diabetes for at least a year who received a prescription for a basal insulin (glargine U-100, glargine U-300, detemir, degludec U-100, degludec U-200, regular U-500, or NPH insulin).

The patients had a mean hemoglobin A1c of 8.4% and a mean basal insulin dose 0.4 units/kg per day. The prevalence of overbasalization was 38.1% for those with hemoglobin A1c above 8%, 42.7% for those with A1c of 9% or above, and 42% with A1c of 10% or greater.

Patient characteristics independently associated with overbasalization were age 35-54 years (odds ratio 1.89), age 65-80 years (0.44), A1c 9% or greater (13.97), and A1c 10% or greater (6.04). Having a prescription for insulin glargine U-100 was associated with a lower overbasalization risk (0.62). In multivariate analysis, only an A1c of 9% or greater remained significant.

Rozalina G. McCoy, MD, an endocrinologist and primary care clinician at the Mayo Clinic, Rochester, Minn., said in an interview that she sees [overbasalization] frequently in patients who are referred to her. "It's kind of that wall that patients with type 2 diabetes hit because their A1c is high but their fasting blood sugars are normal. Sometimes it's assumed that there's a discrepancy, because people don't always think about postprandial hyperglycemia."

She also noted that there has been a push in recent years to simplify regimens, particularly in older patients.

"We really want to avoid rapid-acting insulin in older patients because we're afraid of hypoglycemia, so we start them on basal and keep the noninsulins like metformin and sulfonylureas around. Initially those control the postprandial blood sugar but over time they're no longer enough."

Options Exist for Addressing Postmeal Blood Sugar Highs While Minimizing Lows

While in the past adding premeal insulin was the only option, today there are alternatives for addressing postmeal hyperglycemia, at least in the short term.

Cowart advised that the first step is to have patients self-monitor their blood glucose and titrate their basal insulin to address fasting hyperglycemia first. Once that appropriate dose is reached, if the patient's hemoglobin A1c is still above target, the next step is to evaluate the need for postmeal control.

For patients who are at high cardiovascular risk, the next step might involve adding a sodium-glucose cotransporter 2 inhibitor (SGLT2i) or a glucagon-like peptide 1 receptor agonist (GLP-1RA) instead of premeal insulin. But for patients in whom overbasalization is the main concern, a GLP-1RA might be the better choice since it will have a greater impact on postprandial glucose levels, while an SGLT2i will have more effect on fasting blood sugar, he said.

Another option is to use a fixed-dose combination of basal insulin and a glucagon-like peptide 1 receptor agonist (GLP-1RA), provided there aren't cost or formulary barriers. "We want to use the right combination of drugs and not use too much of one to lead to hypoglycemia," Cowart said.

McCoy doesn't use fixed-dose combinations because they don't allow as much flexibility in dosing. To correct overbasalization, she also recommends adding either a GLP-1RA or SGLT2i instead of premeal insulin. However, she cautions, "you still have to monitor those patients because after a few years it still won't be enough and you'll have to add mealtime insulin."

If cost or lack of coverage prevents a patient's use of SLGT2i/GLP-1RAs, McCoy said that adding just one premeal injection of rapid-acting insulin before the largest meal of the day is one option. Another is to use twice-daily NPH insulin instead of analog basal insulin, since that does offer some postprandial coverage.

Cowart said his approach in cost barrier situations is to try to use patient assistance programs and to look into the patient's formulary to see if there is step therapy or tier considerations, and maybe have a discussion with the insurance company. "We often have to navigate that, and it does take a significant amount of time and could potentially delay patients getting the right therapy when it's warranted. That is an area where there is a particular role for pharmacists in helping to overcome that and get patients on the right drugs," he explained.

Problem May Be Even More Common; Testing Is Key

McCoy said that the A1c cutoff of 8% used to define overbasalization in the study probably resulted in an underestimation of the problem, since many patients are experiencing nighttime hypoglycemia from the basal insulin. The lows bring down their A1c level, but they're still experiencing postmeal highs.

"I think they're missing a lot of people, to be honest. I see a lot of patients with A1cs that aren't that bad, say 7.5%, and their fasting blood sugars are okay, but if you were to put a [continuous glucose monitor] on those patients, invariably there's hypoglycemia at night that no one knew about."

Of course, for insurance reasons, most people with type 2 diabetes don't currently have access to continuous glucose monitors. And often those who are not taking multiple daily injections are limited to one fingerstick test strip a day.

McCoy says that if hypoglycemia is a concern she will write a prior authorization justifying more test strips.

"I state explicitly in my notes why I recommend frequent monitoring. If they're on a sulfonylurea, they should be able to check more frequently because they can have hypoglycemia. Same thing with basal insulin."

McCoy advises that patients test their blood sugar 2 hours after the largest meal on one day, and at other times on different days. "Blood glucose after a meal shouldn't be more than 200 [mg/dL]. If it is, that's not a failure of basal insulin. It's doing its job. You just need a different agent."

Cowart has no disclosures. McCoy receives funding from the National Institutes of Health.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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