Insulin Regimens in Type 1 Diabetes
A 19-year-old man is newly diagnosed with type 1 diabetes after 4 weeks of polyuria, polydipsia, and 6 kg of weight loss. His mild diabetic ketoacidosis has resolved. He is a university student whose meal times vary from day to day and he plays football three evenings a week. HbA1c is 11.4 % (101 mmol/mol). Which of the following is the most appropriate outpatient insulin regimen?
- A.Twice-daily premixed 70/30 insulin before breakfast and dinner
- B.Once-daily basal insulin plus mealtime rapid-acting insulinCorrect
- C.Thrice-daily regular insulin without any basal insulin
- D.Once-daily long-acting insulin alone given at bedtime
Explanation
Type 1 diabetes results in near-total loss of endogenous insulin, confirmed here by a very low C-peptide and positive islet autoantibodies, so replacement must reproduce both the continuous basal secretion that restrains hepatic glucose output overnight and between meals and the sharp prandial peaks that dispose of ingested carbohydrate. The basal-bolus regimen, with a long-acting analogue such as glargine or degludec once daily plus a rapid-acting analogue such as lispro or aspart before each meal, achieves this most physiologically and was shown by the DCCT to reduce retinopathy, nephropathy, and neuropathy compared with conventional therapy. It also offers the flexibility this student needs, since prandial doses can be matched to carbohydrate intake and adjusted around exercise, and continuous subcutaneous insulin infusion by pump is an equivalent intensive alternative. Premixed twice-daily insulin is simpler and may suit patients unable to manage multiple injections, but it forces fixed meal times and carbohydrate amounts and produces more hypoglycaemia and worse HbA1c in type 1 diabetes. Short-acting insulin alone at meals leaves the patient without basal cover, so fasting and overnight glucose rise and ketosis can develop. Long-acting insulin alone provides no prandial coverage and causes large postprandial excursions, and it is a strategy used in type 2 rather than type 1 diabetes. Education on carbohydrate counting, hypoglycaemia recognition, and sick day rules, including never omitting basal insulin, must accompany the regimen. Glucose monitoring by continuous glucose sensor with a target time in range above 70 percent is now standard care.
Why each option
- A.
- Premixed twice-daily insulin requires fixed meal timing and content and yields poorer control with more hypoglycaemia in type 1 diabetes.
- B.
- Correct. A basal-bolus regimen mimics physiological insulin secretion, gives the best glycaemic control, and allows flexible meals and exercise.
- C.
- Prandial insulin without basal cover leaves fasting and overnight periods uncovered and risks ketosis.
- D.
- Basal insulin alone provides no prandial coverage and is inadequate in a patient with essentially no endogenous insulin.
Reference: ADA Standards of Care in Diabetes, 2025
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