Introduction - Starting insulin
Insulin can be prescribed alone or in combination with Metformin, which improves insulin sensitivity.
Ensure your patient’s NDSS registration is updated to indicate insulin treatment, so that she can get insulin needles for free from the pharmacy.
Insulin is safe in pregnancy
When to start insulin:
Insulin is recommended for women with GDM when glucose levels are above target levels on at least 2 occasions in the space of one week – particularly if there is a pattern of regular, recurrent hyperglycemia. It may occur before pre-breakfast or post-meals.
Insulin is a better choice than Metformin in pregnancies where the baby appears small (EFW below 10th percentile), because Metformin interferes with the transplacental provision of nutrients to the fetus.
These insulin options are safe in pregnancy and don’t cross the placenta.
Rapid-acting insulin (Novorapid, Humalog)
This insulin is added to the meal before which the post-meal glucose level is high. The peak of action for these insulins is 1 hour after the injection. Therefore, it is best to give the dose 15 – 30 minutes before the meal, so that the peak coincides with the glucose peak from the absorbed carbohydrate.
Pre-mixed insulin (Novomix 30, Humalog Mix 25, Humalog Mix 50, Mixtard 30/70)
This insulin is a combination of rapid-acting insulin and a slower acting insulin. The rapid-acting insulin controls the glucose levels straight after the meal that it is given (breakfast and dinner), while long-acting insulin controls the pre-meal glucose levels for the next 12-16 hours. It is given once or twice a day – before breakfast and dinner and relies on the patient eating these meals regularly.
It is useful when your patient has high glucose levels before breakfast and after meals regularly, and they prefer to have a simple insulin regimen of two injections rather than a basal bolus insulin regimen that requires 4 or 5 injections a day.
The peak of action for these insulins is 1 hour after the injection. Therefore, it is best to give the dose 15 – 30 minutes before the meal, so that the peak coincides with the glucose peak from the absorbed carbohydrate.
Long acting insulin (Protaphane, Lantus, Levemir)
These insulins have a duration of action of up to 24 hours and control the pre-meal glucose levels. It can be given on its own or it is combined with doses of rapid insulin for mealtimes.
Which insulin to start:
Your choice of insulin will depend on the pattern of high glucose levels and the preferences of the woman with GDM. Pre-mixed insulin provides a convenient option for women who don’t want to inject multiple insulin doses but whose glucose levels are high at multiple time points in the day.
How to adjust the dose:
As the placenta grows, glucose levels may be expected to rise progressively during pregnancy. Once insulin is commenced, the doses may need to be increased once or twice every week. The challenge is to increase the dose for the next week (when glucose levels may rise further) by looking back on the previous weeks’ glucose levels.
If the glucose levels are above target, the insulin dose that was active at that time should be increased by 2 – 4 units.
Please refer mothers to a specialist diabetes antenatal clinic for support in adjusting insulin doses.
How to inject insulin
Insulin treatment is so important to how diabetes is managed, it makes sense to get the technique right. Here are tips for a good insulin injection:
Tips for getting the best effect from the insulin injection:
How to handle insulin
How to dispose of needles
Hypoglycemia (a hypo) is when glucose levels fall below 3.5mmol/L. Normally, glucose levels are a lot lower in pregnancy, so there is no need to worry if glucose levels are lower – particularly if they are asymptomatic. Of course, hypoglycaemia is a side effect of insulin. So, if hypos occur (and recur), it is an indication to reduce the dose of insulin
Reactive hypoglycemia can occur in response to high-sugar or high-GI carbohydrate foods, when the insulin response is exaggerated and delayed. The hypoglycaemic episode itself does not harm the baby, but the sympathetic response and rebound hyperglycemia after the hypo is more problematic. So, aim to prevent hypos and overtreatment of hypos when they do occur.
Symptoms of a hypo include:
Follow these 3 steps to treat a hypo:
Step 1: A small dose of glucose to bring the glucose level up quickly
Choose just one of these options:
Step 2: Recheck your glucose level 15 minutes later to make sure it is coming up above 3.5mmol/L
Step 3: Have a small amount of carbohydrate to keep the glucose level up