My fasting blood glucose ranges from slightly below 100 to 150 in the am - depending how low carb i eat. should i ask my doctor for metformin?

Perhaps: Fasting glucose readings up to 150 is definitively suggestive of insuin resistance, and therefore diabetes. If you can control it with a low carb diet, exercise, weight loss and keep it around 100, you may be better off that way. But if that's not possible, metformin would certainly be a reasonable choice for 1st line therapy.

Consult your doctor: You should have an evaluation to establish if you have diabetes. In case you do, you need to take a more holistic approach rather than demanding drugs. If you are overweight, losing about 10% of your body weight may improve Insulin sensitivity as can physical activity. Your doctor may recommend consulting a nutritionist for better choice of foods. If still needed, metformin may be used.