Right now my ratios are 10% carb, 20% protein and 70% fat. I try to keep my net carbs uner 30 to keep my blood glucose in the lower end of "normal".

If I was to eat 100 g of carbs a day, I might as well eat 300.

Has your doctor given a level to aim for?

I'm at around 100g. My fasting blood sugar went from 111 to 84. As long as you're eating at a calorie deficit, you're fine.

Around 1g protein per kg of body weight, rest in fat. Percentages don't matter. (On my phone, sorry if I sound curt.)

Back on my computer now, so I can give you a more complete answer.

Carbs raise blood sugar. Blood sugar raises insulin levels. So as a pre-diabetic, your goal should be two-fold:

1) Reduce your blood sugar levels. This happens by simply cutting carbs. How low do you need to go? Really, the only way to determine that is by testing your blood sugar at multiple times after a meal. This site has excellent info:
bloodsugar101.com/

2) Increase insulin sensitivity. This isn't completely understood yet, but the primary goal should be to reduce body fat (especially visceral fat). That requires a calorie deficit, and that often comes naturally with low carb.

With 100g/d of carbs, you are barely meeting your brain's requirement of daily glucose, so even at this relatively high intake compared to the hard-core keto folk, you will deplete your glycogen reserves, and you'll even start making ketones.

But unlike the hard-core keto folks, we probably can't become keto-adapted at this level.

What is keto-adapted? It basically means you grow more mitochondria after about 3 weeks of being glycogen depleted. It's hard to stay depleted at 100g. Your body will replenish glycogen stores whenever it has the chance. At 20g, it'd never have the chance.

So a level of 100g/d of carbs *might* give you the benefits you need in terms of blood sugar control, weight loss, and insulin sensitivity. It did for me. It won't give you the metabolic or brain benefits of a ketogenic diet.

If you stick with adequate protein (around 1g per kg) and the rest in fat, you're following essentially the same game plan as the keto folk. You can then adjust the carb intake to whatever works for you. If you go below 50g or so for about 3 weeks, you'll probably become keto-adapted and enjoy all of the fringe benefits.

Or stay below 100g or so, and you may enjoy most of the health benefits and find it a much more sustainable way of eating.

My macros are 5/20/75 at 1400-1500 calories. MFP calculator says 1800, but I went for the 30% deficit.