I hope the antibiotic is not a fluoroquinolone!

Our bodies make carnitine but it can get low with age.
There is some carnitine in meats....but if you are low, it wouldn't hurt to take as a supplement. Start at 500mg a day acetyl carnitine, and you might feel better.

Carnitine helps the mitochondria use fatty acids when glucose is low. So energy needs can still be met.

110 fasting glucose suggests insulin resistance. Not high enough to be diabetic yet. But when glucose cannot get into cells, the cells cannot produce energy...another reason to use carnitine.

Two major families of drugs can deplete carnitine in the body.
Depakote (valproic acid) and the antivirals used in HIV treatments.

Here is a monograph on Carnitine;
http://www.umm.edu/altmed/articles/c...e-l-000291.htm

The muscle biopsy is to look for mitochondrial damage. Some people carry the genes for mito disorders, and muscle weakness is one sign of that.