Dear fellow insulin addicts!
I have so far had a rather rich worldwide job/traveling/sporting and reasonable easy life with my diabetes. Always on top of it and in tight control. Here now a couple of years back (yep, sorry this took my surplus power away, so have not been here on the forum for some time), I started suddenly within just a few days/weeks time to experience drastic muscle pain and fatigue while at times having symptoms aka 'brain fog' with challenge to really focus on solving complex problems etc. which is part of my daily job. The kind of pain was not typical diabetic neuropathic, as it was in the large muscle groups in legs and later also in the upper arms.
Have over the past 18 months gone through virtually everything a human body can be tested for:
Neurology, psychiatry, brain/body cancer checks with MRIs scans etc, rheumatology, rare genetic muscle/neuro diseases, etc etc.
Nothing came out with any hints of anything wrong, except that I was low on D vitamins and that the electro myography indicated a lower amplitude but prolonged signal to the muscle cells compared to normal when contracting. So no fatal disease of any kind but also no real explanation or resolution to my misery. The rheumatologist recommend I started taking a few supplements to ensure all vitamin/minerals/anti oxidants were all boosted to the max, so done that for some 3-4 mths by now. The muscle pains have mainly gone, but the fatigue and occasional 'brain fog' still comes and goes. The werid thing is I have not been able to connect it with anything really regarding my life/activities as such. And it comes more severely in some unpredictable periods. E.g. as soon as I wake up I can say if this is going to be a tough day with fatigue or not. The muscles are getting this burning sensation like lactic acid building up, like when you run 10 miles or go downhill skiing on moguls. And it comes then very quickly, like when just running up 1 flight of stairs or holding your mobile phone to your ear for 3 minutes...
In my desperate search for answers I of course consider the IDDM Type1 as a possible avenue. I noticed that in same period I suddenly have become allergic to something (sneezing, running nose, without being positive in any of the allergy tests at the hospital) and also I suddenly had a rash of Vitiligo, where some minor spots on my skin now has no color pigment. Never had any of those before. But all has stabilized of this. It simply just started all at the same time, as like ones immune system went crazy for a period of time.
I then came across a couple of posts on this forum written 5-8 years back, where some had written about similar symptoms on muscle pain, fatigue and 'brain fog'. And that they had terminated using analogue insulins. As I am a sceptic realistic but sincerely willing to learn more, I would enjoy to hear from such individuals again today, to hear if their improvements were sustained after they switched to either human or porcine insulin?
Muscle pain and fatigue is unfortunately a very common symptom for many various diseases, so challenging to weed out the 'relevant from the noise'. But I am very eager and willing to try to drop my love for NovoRapid and Lantus, if old fashioned insulins can give me my life back!

I suppose the only way to rule out the possibility that your insulin may be the cause is to change it for a few months and see if there's any releif, you could return to your preferred regime if it turns out that it was not responsible.
The human body is a funny old machine, it can tolerate some things for years before it starts complaining. Good luck.

Very familiar I also often had muscle pain when I was doing sports. I was always skinny and wanted to gain some muscle mass, but even because of my illness, I could not exercise properly, I constantly had very severe pain in my muscles. I solved this problem with aquatec this is the aqua test steroid it allowed me to gain weight without putting much effort!!!