This problem actually happened to me. A few years ago I started feeling incredibly lethargic. I would wake up with no energy. It was like sleep had done nothing for me. I didn't know what was wrong, but I felt horrible.
After around two weeks I went to the doctor. A blood test was done and it showed I had low vitamin D (26 ng/mL). After about a week of supplementation I felt normal again. It's easy to forget to go outside, and if you're a programmer and feel low energy, vitamin D is definitely something to look into.
20 is the lower limit of normal per US guidelines, though some specialty societies have their low threshold set at 30.
At any rate, you are unlikely to have any calcium metabolism deficits at 26 and it's unlikely to have been a cause of any symptom in an otherwise healthy adult.
Hrm, I may have the "ng/mL" part wrong then, or I may just be sensitive to low levels. All I remember is the number and that he said I was low. Supplementation definitely resolved my problems though.
26 ng/mL is not that bad actually... I once was tested at 12 ng/mL, and that was only after I asked for it when I fractured my left wrist for the second time in one year.
Personally I was so low down in D I also had neuropathic symptoms -- like your hand or parts of face falling asleep, light-headedness and muscle twitches and tremors. That all went even after some D vitamin injections.
After around two weeks I went to the doctor. A blood test was done and it showed I had low vitamin D (26 ng/mL). After about a week of supplementation I felt normal again. It's easy to forget to go outside, and if you're a programmer and feel low energy, vitamin D is definitely something to look into.