Insulin Therapy Guidelines for Type 2 Diabetes
Preference for GLP‑1 Receptor Agonists vs Insulin
- GLP‑1 receptor agonists (including dual GIP/GLP‑1 agents) are the preferred injectable therapy for most adults with type 2 diabetes, except when there is clear insulin deficiency, severe hyperglycemia (A1C > 10 % or glucose ≥ 300 mg/dL), or symptomatic hyperglycemia. [1][2]3
Indications for Initiating Insulin
- Immediate insulin initiation is warranted in patients showing evidence of ongoing catabolism (e.g., unexpected weight loss, ketosis). 4
- Insulin should be added when A1C ≥ 8.5 % despite optimized oral therapy, because further benefit from non‑insulin agents is unlikely. 5
- Progressive β‑cell failure despite combination oral therapy also signals the need for insulin. 5
Initiation and Dosing Strategies
- Start basal insulin at 0.1–0.2 U/kg/day (≈10 U for most adults); increase to 0.3–0.4 U/kg/day if the patient presents with severe hyperglycemia (glucose > 300 mg/dL). [5][4]
Basal Insulin Selection and Administration
- Long‑acting analogues (glargine, detemir, degludec) are associated with less nocturnal hypoglycemia than NPH insulin. [5][6]
- NPH insulin is a lower‑cost alternative but carries a higher risk of hypoglycemia. [7][4]
- Basal insulin may be administered at bedtime or timed according to the individual’s glucose profile. 5
Titration Protocols
- Increase the basal dose by 2–4 U (or 10–15 % of the current dose) once or twice weekly until fasting glucose reaches 80–130 mg/dL. [5][4]
Combination with Oral Agents
- Continue metformin when insulin is started; it reduces weight gain, lowers insulin requirements, and lessens hypoglycemia risk compared with insulin alone. [8][2]
- Reduce or discontinue sulfonylureas and meglitinides at insulin initiation to minimize hypoglycemia. [1][2]
- When insulin is used, adding a GLP‑1 RA (or dual GIP/GLP‑1 RA) is recommended for better glycemic control, weight benefit, and reduced hypoglycemia; insulin doses are often reduced after adding the GLP‑1 RA. [1][2]3
Adding Prandial (Mealtime) Insulin
- Add prandial insulin if the basal dose exceeds 0.5 U/kg/day, indicating over‑basalization. [5][2]
- Add prandial insulin when post‑prandial glucose excursions consistently exceed 180 mg/dL. 6
- Initiate prandial insulin with 4 U or ≈10 % of the basal dose before the largest meal using rapid‑acting analogues (lispro, aspart, glulisine). [8][4]
- Alternatively, switch to twice‑daily premixed insulin (70/30 NPH/regular or analogue mixes) if appropriate. 8
Monitoring for Over‑Basalization
- Watch for a large bedtime‑to‑morning glucose differential (indicative of excess basal insulin). 6
- High glycemic variability also signals over‑basalization. 5
Special Populations & Cost Considerations
Cardiovascular & Renal Disease
- In patients with heart failure, prioritize SGLT2 inhibitors over insulin. [1][2]
- For chronic kidney disease with eGFR 20–60 mL/min/1.73 m², use SGLT2 inhibitors first. [1][2]
- In advanced CKD (eGFR < 30 mL/min/1.73 m²), GLP‑1 RA is preferred to insulin. [1][2]
Cost
- Human insulin (NPH and regular) remains an acceptable lower‑cost option for patients with financial barriers, despite higher hypoglycemia risk and less dosing flexibility. [1][7]2
Clinical Pitfalls to Avoid
- Do not postpone insulin intensification; prolonged uncontrolled hyperglycemia must be avoided. 5
- Do not use insulin as a threat; present it as a necessary step in disease progression, not as punishment. [9][10]
- Do not combine DPP‑4 inhibitors with GLP‑1 RA, as no additional benefit is observed. 3
- Avoid saxagliptin and alogliptin in patients with heart failure due to FDA‑issued heart‑failure risk warnings. 4
Patient Education Essentials
- Provide instruction on sick‑day management for patients on insulin. 6
- Teach self‑titration algorithms so patients can safely adjust basal doses. 5