3.5 yes so ate and tested 15 mins later and bs had raised. I knew something was wrong which is why I tested.
Yes, as Alison mentions, my numbers tend to naturally run quite low these days, and numbers like you saw the other day are not unusual or of concern to me. It just seems to be how my body works these days.
Before we eat, our bloods are x-y, after eating they y-z (numbers unimportant, but likely to be relatively consistent, within that range), with out diet largely managing the highs and our livers managing the lower threshold. In other words,as our bodies go low, our liver releases some glucose to keep us in our comfort zone.
Eating is a bit like juggling we can handle two or three balls and have a routine meaning we can keep the juggling going for periods - so long as nothing disrupts or distracts us, in which case we drop a ball.
My speculation on your situation would be that your body has got used to running in a range (whatever that is). Your routine was disrupted a bit, and you had a higher carb lunch that usual, so at it's peak your bloods were likely a bit higher, but then started falling faster than usual. A sharp peak can lead to a sharp fall. If that sharper fall is fast enough it's like the juggling ball hitting the ceiling and coming down faster than it went up and we don't catch it.
When we move outside our running ranges we can feel uncomfortable; likened to a hypo, but if we are not taking an blood glucose lowering meds, that low is very, very unlikely to be a medically concerning low.
On the odd occasion it happens to me (whether by a carb hit, or by just getting rather too hungry), if I am about to eat, I just crack on and enjoy my food. If food is a bit further off, I just have a cup of tea with some milk, which just nudges me up a bit and gives my system something to work on.
I don't "treat" the low in a traditional way as, in my view, I would run the risk of repeating the cycle.
3.5 is quite low, and certainly the first few times one sees those numbers it can be alarming, but I'd urge you to just monitor it for now. If you feel rough at those numbers do something about it, but be gentle. If you feel fine, it's up to you what you want to do.
All of that assumes you arre not taking blood glucose lowering meds (which doesn't include Metforimin). Were you taking such drugs my view would have differed.