leptin concentration starts low in the morning and rises throught the day to peaks at about 2am with a typical range of 4-16 ng/ml. i think the pattern is the important aspect. your level is within this range, but what it means is dependent on the time of day it was sampled i would guess.

First of all, congratulations on significantly lowering your fasting glucose and insulin levels. It seems that you're making a lot of good dietary choices in order to see those improvements. Dr. Rosedale (drrosedale.com), who I respect a great deal sugests that optimal range for leptin is 4-6 ng/dL, glucose 70-85, HbgA1C <5.4, and insulin <10 IU/mL. If your insulin remains low you shouldn't accumulate fat, but your glucose is still high, which could suggest that you're eating too much carb and/or protein. Excess protein beyond what the body needs will be converted to glucose in the liver via gluconeogenesis. If you've been insulin and leptin resistent for years (chronically high hormone levels leading to cells inability to receive their signals) it will take several weeks to convert from sugar burning to fat burning. I find that if I drop out of keytosis for long (>50g carbs/day) I gain fat quickly. Over the past year I've lost 40lbs of fat (196 down to 156 lbs now) and I see how my 40 years of poor diet have damaged my metabolism. I find that I have to stay VLC (<30g/day), with moderate protein (no more than 20g/meal, 60g/day), and getting most of my calories from healthy fats (70-80%) to stay lean. Everyone's metabolism is in a different state of health, but if you eat 80% calories from fat you will get very lean (or at for sure the leanest you can possibly be).