Hi Hale!
I have the same issue sometimes - it's bizarre how the numbers can spike with the same food and insulin that's normally OK. There's a couple of things that I've put it down to over the years I've dealt with it, but i don't have any evidence.
1. Something is making you more insulin-resistant than usual so your insulin isn't work properly - for me, that's usually the week before my period. I have to increase doses, but that does cause the odd hypo which I stave off with a strategically-timed finger of dark chocolate kit kat (about 7g carb). For some reason, around this time, my Apidra seems to work more slowly - but it does work in the end!
2. Some kind of cold/bug/virus/infection/pain etc is on its way - usually a migraine about to start for me - although to be fair, that might be connected with point 1 above!
3. Your insulin has been out of the fridge for a fairly long period of time (basal or bolus) and needs chucking away and a fresh one using. I use fairly small doses and my cartridges last the full 30 days they are allowed to be in the pen - most people's don't. So, after a couple of these types of episodes, I took the decision to discard insulin when it's been in the pen for more than 20 days and start new cartridges. I think it loses its potency and/or changes its absorption abilities, although I have no evidence.
4. Your pen isn't working properly - I don't think the pens are as accurate on very low doses and any slight issues with them are more noticeable. I guess if you are injecting a sizeable dose, the force of the liquid forces the dose out through any minor blockages, but I only use 1.5 units with my lunch and that's the one i seem to have more problems with. That might just be a load of rubbish though LOL.
Anyway, you get my drift - so many reasons it could be happening. Try changing one of the things you can e.g. the insulin or the pen and see if it makes any difference.
Smidge