Consistency of effectiveness of individual insulin pens

[ABC62]

I have Type 2 and take insulin including fast acting. My glucose levels are generally well controlled and I've got the insulin doses right and hit the 75% in range target but on occasions measurements go unexpectedly all over the place when I have not eaten differently. This happened previously when starting a new pen. Has anyone experienced similar in that the insulin suddenly doesn't work as expected? When it happened before I carried on with the 'dodgy' pen for a week then disposed of it, started a new one ands my levels went back to what I expected. This week I'm getting similar with levels spiking quite high and co-incidentally I started a new pen.

 

[Deleted member 527103]

It is possible that insulin has not been kept properly which will affect the effectiveness of the insulin although this is rare and very unlikely if it is from the same batch.
Over the last week or so, for me, I would put the change of effectiveness down to the weather. But there are many other things which can affect our blood sugars beyond insulin and food.

I notice you mention that you change your insulin pen. Is that because you are using single use pens?
I highly recommend the reusable pens. These are far more robust, the cartridges take up less space in the fridge (and luggage when travelling), if using NovoNordisk (NovoRapid, Fiasp, Levemir, Tresiba) insulin, you can get them for half units with a electronic reminder when you last took your insulin. And you create far less waste so much better for the environment.