You might want to cross-post this in general parenting or Health & Healing. There is an epidemic of type 2 diabetes among children these days and that means that many are dealing with the pre-diabetic conditions in toddlers complete unaware that this is the problem (I see a lot of this in my own practice).
Also, metformin will lower your sugar level so that your insulin levels don't get so high. It's a help, but it's not fixing the problem. I know this because I've btdt and am now a step from full-blown diabetes. Granted, it's taken far longer to get there, but I'm still there.
You might want to look at the book "The Blood Sugar Solution" by Dr. Mark Hyman. It's a plan that attempts to reverse the problem. It's strict, but it looks good. I know that he recommends a supplement (maybe on the accompanying website) called MetaGlycemx by MetaGenics. You should know that this does the same thing metformin does, but in a natural form. So I don't really love that it's being recommended--it's like saying "do all this work but then be on the meds anyway". I was on MetaGlycemx for many years and it actually worked for me better than metformin in keeping my insulin levels down.
You may NEED the help that metformin or MetaGlycemx can give you just to get things going and get stable. I'm not saying "don't take it". I'm saying "understand the condition and what this is going to do so that you know how to proceed long-term"... kwim?
Also, my condition became physically obvious around age 13 although it was not properly diagnosed until I was nearly 30yo. I suffered nearly debilitating mental health problems as a result of the insulin problem.
Best to you.