Hello resage, I’ve had idiopathic SFN for 3 years, I take 300 mg. gabapentin at bedtime which puts me (luckily) to sleep, when I still can’t fall asleep I take 10 mg. melatonin. If the 600 mg. gaba doesn’t help you, you say you have no pain or tingling which is what gaba is good for, I would take consider taking supplements which can benefit your nerves at this early stage. I have been taking R-alpha lipoic acid, acetyl-l-carnitine, B12 and B complex plus a multi vitamins. I don’t drink alcohol, limit my carbs and sugars and exercise. My SFN has been greatly reduced over the past 3 years due to this practice I believe. I have never had a biopsy, my neurologist said she would treat the same (with gabapentin) regardless of result. Helen