From the Guidelines
Yes, you can start a patient with an HbA1c of 16.1% on 20 units of basal insulin while they continue taking metformin 500 mg ER, as the starting dose can be estimated based on body weight (0.1–0.2 units/kg/day) and the degree of hyperglycemia, with individualized titration over days to weeks as needed 1. This approach is appropriate given the significantly elevated HbA1c, which indicates poor glycemic control that requires intensification of therapy.
- The recommended starting dose for basal insulin is typically 10 units daily or 0.1-0.2 units/kg/day, so 20 units is reasonable for most adults.
- Administer the basal insulin (such as insulin glargine, detemir, or degludec) once daily, preferably at the same time each day.
- The patient should continue taking metformin 500 mg ER as prescribed, as it works synergistically with insulin by reducing insulin resistance.
- Consider increasing the metformin dose to 1000-2000 mg daily if tolerated, as higher doses may provide better glycemic control.
- Instruct the patient on proper insulin injection technique, blood glucose monitoring (ideally before breakfast and dinner daily), and hypoglycemia recognition and management.
- The insulin dose should be titrated by increasing by 2-4 units every 3-7 days until fasting blood glucose targets (typically 80-130 mg/dL) are achieved. This combination therapy addresses both insulin resistance (with metformin) and insulin deficiency (with basal insulin), which is necessary for patients with such poorly controlled diabetes, as supported by the standards of medical care in diabetes-2021 1.
From the Research
Initiating Basal Insulin Therapy
- The decision to start a patient with a hemoglobin A1c (HbA1c) level of 16.1% on 20 units of basal insulin, while they are already on metformin 500 mg extended release (ER), should be based on clinical guidelines and the patient's specific needs 2, 3, 4.
- According to the EADSG Guidelines, insulin therapy is considered for patients with type 2 diabetes mellitus (T2DM) when HbA1c is ≥ 7.5% (≥ 58 mmol/mol), and is essential for treatment in those with HbA1c ≥ 10% (≥ 86 mmol/mol) when diet, physical activity, and other antihyperglycemic agents have been optimally used 2.
- The American Family Physician suggests that insulin therapy may be initiated as augmentation, starting at 0.3 unit per kg, or as replacement, starting at 0.6 to 1.0 unit per kg, for patients with type 2 diabetes mellitus and an initial A1C level greater than 9 percent, or if diabetes is uncontrolled despite optimal oral glycemic therapy 3.
- A study published in The American Journal of Medicine emphasizes the importance of patient education and the choice of available basal insulins, as well as the necessity to optimize basal insulin dosage by self-titration 4.
Dosage and Titration
- The initial dosage of basal insulin can vary depending on the patient's needs and the specific insulin used, but a common starting point is 0.3 unit per kg for augmentation therapy or 0.6 to 1.0 unit per kg for replacement therapy 3.
- Fasting plasma glucose (FPG) values should be used to titrate basal insulin, whereas both FPG and postprandial glucose (PPG) values should be used to titrate mealtime insulin 2.
- The goal of titration is to achieve optimal glycemic control while minimizing the risk of hypoglycemia and other adverse effects 2, 3, 4.
Combination Therapy with Metformin
- Metformin combined with insulin is associated with decreased weight gain, lower insulin dose, and less hypoglycemia when compared with insulin alone 2.
- Oral medications, including metformin, should not be abruptly discontinued when starting insulin therapy due to the risk of rebound hyperglycemia 2.
- Continuing metformin therapy, if possible, is recommended because it has been proven to reduce all-cause mortality and cardiovascular events in overweight patients with diabetes 3.