Hi Sarah,
They're horrible aren't they? Unfortunately, they're a fact of life if you are diabetic. There are some rules that I have.
First, I always have dextro tablets on me. This is the most important rule - always have a source of fast acting carbohydrates with you. I take three to five if my BG is in the 3 - 4 mmol/l range.
Second, I always have a bottle of lucozade in my house and take it with me if I'm staying somewhere else. Lucozade is the best treatment for a bad hypo, I.e. < 3 mmol/l. Fortunately, I've not had to use it for many months.
Third, always carry your glucose meter with you. Hypo signs can sometimes be subtle and easy to miss. Always test if you think you are hypo.
Always test two hours after eating as this is around the peak of the work rate of fast acting insulin.
Hypos must be taken seriously, BGs < 2 mmol/l can mean loss if conciousness.
Hope this helps.