Why Lows Happen in GDM
Reviewed by CDE Mehandi Sharma · Updated
If you are having lows, something specific is usually causing them, and it can generally be fixed.
The recognised causes are:
- Insulin taken and then the meal delayed, reduced or missed.
- Not enough carbohydrate for the dose given.
- Fasting while continuing insulin.
- More activity than usual — during it, and for some hours afterwards.
- Being unwell, especially with vomiting.
Pregnancy adds two of its own. Nausea and vomiting can mean a meal you dosed for does not stay down. And insulin needs change as the pregnancy progresses, so a dose that was correct three weeks ago may now be too much — most notably right after delivery, when requirements fall sharply.
Under-eating out of fear of high readings is another cause worth naming, because it is common and it is treatable by eating properly rather than by carrying more glucose.
What to do about a pattern: note when the lows happen. Lows at the same time each day point at a particular dose. Lows after activity point at timing. Lows after vomiting point at a sick-day plan.
Take that pattern to your team promptly. Repeated lows in pregnancy are a reason to revise the regimen, not to manage privately with extra snacks.