•Severe hyperglycemia on presentation or difficulty distinguishing type of diabetes – Insulin is indicated as initial treatment for some patients with type 2 diabetes, depending on the severity of the baseline metabolic disturbance (eg, insulin is always indicated for patients presenting with symptomatic [eg, weight loss] or severe hyperglycemia with ketonuria, or in patients in whom it is difficult to distinguish type 1 from type 2 diabetes).
•Persistent hyperglycemia on oral therapy – After a successful initial response to oral therapy, most patients have worsening glycemia over time and require additional therapy (add a second oral or injectable agent, including insulin, or switch to insulin). For many patients, we prefer insulin or a glucagon-like peptide 1 (GLP-1) receptor agonist (if the patient is not catabolic) for a second-line medication. Insulin is always effective and is preferred in insulin-deficient, catabolic diabetes (eg, polyuria, polydipsia, weight loss).
●Initial basal insulin – For patients who are initiating insulin (in addition to oral agents, in place of oral agents, or as initial treatment), we suggest initiating basal, rather than prandial, insulin (Grade 2B). This is predominantly due to a lower risk of hypoglycemia and greater convenience and simplicity for patients who are using insulin for the first time.
•Choice of basal insulin – Either insulin neutral protamine Hagedorn (NPH) or detemir given at bedtime or insulin glargine or degludec given in the morning or at bedtime is a reasonable initial regimen.
•Initial dose and adjustment of basal insulin – The initial dose for NPH, detemir, glargine, or degludec is 0.2 units per kg (minimum 10 units) subcutaneously daily. Subsequent modifications can be made according to fasting glucose and A1C values, until the fasting glucose is in the target range (80 to 130 mg/dL [3.9 to 7.2 mmol/L] in young patients and with higher fasting glucose targets for older patients and those at risk of hypoglycemia)
●Persistent elevation in A1C with fasting glucose in targetrange – Among patients who are taking insulin and have A1C values above the desired target with fasting glucose levels in the target range, dietary and exercise patterns should be reviewed. We advise the patient to check fingerstick capillary glucose levels fasting, pre-lunch, pre-dinner, and before bed while the regimen is being adjusted. Prandial insulin is often started as a single injection before the largest meal of the day, but many strategies are possible.
●Combining basal and prandial insulin – For patients with type 2 diabetes who require prandial insulin, either short- (regular) or rapid-acting insulin can be given. The ability to inject the rapid-acting insulins 10 to 15 minutes before meals (as opposed to the 30 to 45 minutes before the meal recommended for short-acting insulins) may provide improved convenience for patients. In this setting of multiple daily insulin injections, oral agents other than metformin are usually discontinued to reduce polypharmacy and cost. Oral or injectable GLP-1 receptor agonists may also be continued.
●Premixed insulin – For patients with type 2 diabetes who require prandial insulin, we suggest not using premixed insulin initially. The goal is to adjust the dose of short-acting or rapid-acting insulin immediately prior to a meal, and therefore, we prefer to keep basal and pre-meal insulin injections separate and adjust them independently. However, premixed insulin is a reasonable option for patients with type 2 diabetes who are doing well on a stable, fixed ratio, especially if the meal pattern matches the kinetics of the premixed insulin (eg, large breakfast and dinner with small or low-carbohydrate lunch).
●Troubleshooting – Monitoring for complications of insulin (including hypoglycemia and weight gain) and identifying and addressing the triggers, if present (missed meals, alcohol, and unanticipated exercise for the former and dietary indiscretion and obligate snacking for the latter) should be performed at every visit to permit insulin regimen adjustment. Provide patient education at every visit to minimize these adverse effects of insulin therapy.
