Low insulin normal glucose

My fasting insulin level is very low (below 2 mE/L). I measured it first 2 years ago and it was 3,9 mE/L (ref. range 2-29,1). Carbs intake was 200g per day back then, mostly from low GI foods, absolutely no sugars.

Last week my fasting insulin was below 2 mE/L. These weeks I have been eating about 350g of carbs per day (from 450g of brown rice daily, 100g of oats, 1 piece of fruit, so still low GI foods). 350g carbs per day should by my opinion trigger higher insulin, but I have been taking last weeks also high doses of alpha lipoic acid + acetyl l carnitine which are both known to improve insulin resistance and lower insulin. In my case it seems they lowered insulin too much.

From the day I started alpha lipoic acid and carnitine my situation started to get even worse than before:

-tired and sleepy
-impossible to gain any weight
-bad blood circulation
-very difficult to do any weight lifting training

I have been felling very tired for last 4 years and my doctor thinks it is just depression which I don't believe. I checked thyroid and testosterone levels and they are fine.

Do anybody have any idea or thoughts if my symptoms could be related to low insulin levels even if my glucose is always normal?

It is done in laboratory, I ordered it together with some other tests.