Hi,
I would suspect the Lantus, it's notorious for causing joint and muscle pain.
I developed pains in my arms, shoulders and chest area within months of going on Lantus. I was referred to a physiotherapist at my local hospital who then referred me to a rheumatologist. He suspected fibromyalgia and referred me to a specialist-who turned out to be a quack,and confirmed it- it was all rubbish as I since discovered.
It took another 4 years and many other side-effects for me to realise it was Lantus. Needless to say since coming off it and changing to porcine insulin, I no longer have the problem,or the other side-effects which included debilitating exhaustion, lousy BG conrol, and feeling like I was being poisoned-I actually accused my husband of poisoning me, the poor man.
I've since discovered that many people have suffered similar side-effects on Lantus.
It makes me wonder how many other people are being mis-diagnosed with conditions as a result of the side effects of synthetic insulins or other medications.
Best of luck
Jus