What Causes Lows in Type 1
Reviewed by CDE Mehandi Sharma · Updated
In Type 1, low blood sugar is not random. It nearly always has a cause you can identify, and identifying it is how you stop it happening again.
The recognised causes are:
- Too much insulin for the food, or a dose taken and the meal then delayed or missed.
- Not enough carbohydrate for the insulin taken.
- Fasting while continuing insulin.
- More physical activity than usual — during it, and for hours afterwards.
- Alcohol, particularly on an empty stomach.
- Being unwell.
Two more worth adding. An injection into a site that is overused or lumpy can absorb unpredictably. And reduced kidney function changes how long insulin lasts, so a dose that was right before can become too strong.
The practical point is to treat a repeated low as information rather than bad luck. Lows at the same time of day point at a specific dose. Lows after exercise point at activity planning. Lows overnight point at background insulin or a bedtime snack.
Tell your team about lows even when you handled them. Frequent lows are a reason to revise your regimen, and hiding them means the regimen never gets fixed.