Synopsis
Match insulin pharmacology and delivery to glucose patterns, titrate safely, and prevent hypoglycaemia, ketoacidosis, device and concentrated-insulin errors.
- Rapid-acting analogues cover meals and corrections; short-acting human insulin has slower onset and longer meal-related action, so timing is not interchangeable.
- Intermediate NPH and long- or ultra-long analogues provide basal insulin; basal controls fasting hepatic glucose output and must not be used repeatedly to correct post-meal excursions.
- Basal–bolus multiple daily injection is the standard flexible regimen for most adults with type 1 diabetes; pump and hybrid closed-loop options require structured training and backup plans.
- In type 2 diabetes, start insulin when symptomatic or catabolic hyperglycaemia demands it or when agreed targets remain unmet; a basal regimen is often the simplest entry point.
- Titrate basal insulin from repeated fasting patterns, mealtime insulin from the corresponding post-meal or next-premeal pattern, and corrections from an individually derived sensitivity factor.
- Recurrent overnight hypoglycaemia with high morning glucose may reflect rebound, basal excess or late food; examine overnight data rather than increasing insulin automatically.
- Lipohypertrophy, repeated sites, poor mixing of cloudy insulin, storage damage and needle or cannula problems produce erratic glucose and mimic an incorrect dose.
- Prescribe insulin by brand, concentration, device and dose in full units; never abbreviate units to U or IU, and never withdraw concentrated insulin from a pen with a syringe.
- Insulin detemir supply is expected to end in the UK in December 2026; transition must follow current ABCD guidance with individual dose review, not unit-for-unit assumption.
Key red flags
Falling glucose overnight or between meals, recurrent fasting lows and a need to snack without hunger suggest basal dose exceeds background requirement, especially after weight or renal change.
Unexplained rising glucose and ketones in a pump user can progress quickly because only rapid-acting insulin is present. Inspect cannula, tubing, reservoir and infusion site and use the emergency backup plan.
Confusion, seizure, loss of consciousness or need for another person's help requires rescue treatment, emergency assessment when indicated and urgent regimen, awareness and driving review.
A new pen colour, unfamiliar concentration, missing meal dose or accidental rapid-acting injection instead of basal can cause prolonged harm; identify exact product and time immediately.
Investigation priorities
Link fasting, meals, exercise and overnight patterns to each insulin component.
Management branches
Confirmed insulin-deficient type 1 diabetes requiring lifelong insulin.
- Offer structured education and multiple daily basal–bolus injections using analogue insulin, or assess pump and hybrid closed-loop eligibility and preference through the specialist service.
- Teach carbohydrate ratios, correction sensitivity, active insulin, injection or infusion technique, ketone rules, hypoglycaemia, exercise, alcohol, driving and backup supplies.
- Titrate components from reproducible patterns while protecting basal coverage; a pump user needs written doses and available pens for immediate conversion if delivery fails.
- Review severe hypoglycaemia, recurrent ketones, high variability or treatment distress promptly and escalate technology or psychological support rather than blaming the user.