I am trying to understand how long insulin lasts in the bloodstream. Does anyone know — after a ‘bit’ of insulin has reacted with a ‘bit’ of sugar is it neutralised? Or does it keep on working until its time runs out? In other words, if my child is high at her morning shot will that use up her insulin faster and she’ll probably need extra insulin later, or will the insulin just keep going? We’re not yet using Humalog and giving extra R in the morning won’t help the high — it just causes lows later!

It’s not an easy task to describe how insulin works.

Regular insulin has an half-life in the blood of about 10 minutes, but its clinical prolonged action depends on its prolonged absorption time from the various injection sites, each of them having quite different and variable absorption characteristics.

For the slow-acting insulins, such as NPH or Ultralente, the absorption time is much more prolonged depending upon the different insulins being slower as insulin lasts longer. In order to avoid fasting hyperglycemia in your child, bedtime slow-acting insulin should be present in large enough amounts to last until next morning: if not, its waning is the most important cause of elevated fasting blood sugar.

Ask your team about appropriate insulin adjustments.

MS