It isn't always about keto and diabetes, although I think it is usually about hormones (thyroid is a biggie, as mentioned above).
Also menopause and oestrogen/progesterone balance.
In my case my hair was going haywire in my 30s. Dry, crinkly, breaking, falling out. Did some heavy duty reading on it, including a book called 'What your doc doesn't tell you about menopause', which highlighted that the hormonal changes leading into menopause often start in our 30s, not our 40s.
Anyway, eventually I got diagnosed with a benign tumour of the pituitry gland, and been on medication to (partially) block the production of prolactin, ever since. It took about a year after the treatment started for my hair to go back to normal, and it has stayed that way since. Except for the colour change to grey, of course. lol. Been eating low carb and keto for all that time, and not aware that diet or bgs have had an impact.
So I suppose what I am saying is that don't assume it is just keto. Could be a lot of different other stuff going on, some of which just needs a diagnosis and treatment to resolve.