I'm not on medication either, and have brought my levels right down by just sticking to my reduced carb, portion controlled way of eating. I still eat carbs, but, with the benefit a food diary (myfitnesspal) and recording my bloods, I have identified those I tolerate and those affecting my numbers adversely. I swim every day and generally am pretty active.
Having built up some knowledge, I now just test each morning, and before and after my main meal, or if I am eating something that may have "interesting" effects on my bloods.
Yesterday was:
Pre-breakfast: 4.2. - Breakfast was jumbo oats, with some fibre sprinkled over, with semi-skimmed milk
After breakfast - no test, but this breakfast usually raises the reading by 0.7, at 2 hours
Lunch - small portion of mackerel in a spicy tomato sauce, with a rocket based salad, left over from the previous evening. No test, but this lunch usually results in bloods falling at the 2 hour point.
Pre-dinner 4.3 - dinner was paella with proper bomba rice. This is the first full rice paella for a while, I had been having half rice, half cauliflower rice for a while, so was experimenting. Paella is one of my favourite quick, filling meals.
Post-dinner - 5.1. Quite happy with that.
As my numbers reduced, I found they would be stable for a short while, then step down a notch or two, and stay there. Now I have to ensure I don't reverse those trends in my experimentation!
In my view, the most important things are your records or food and readings, and a consistent approach.
You'll get there.