Why am I suddenly going low very quickly?

I've had two severe lows during/after meals today and I don't know what's causing my bg to drop so rapidly. What increases insulin absorption rate? I can't think of anything I've done differently from any other day. Both times I was eating before injecting (as opposed to usually eating after), and it still tanked me within like 30 minutes. I don't think I hit a muscle, especially not twice.