If I'm understanding you correctly
@dwnunder you believe you are prediabetic or you were prediabetic? From your HbAc1 number 5.5 % that is in the normal range. So your Dr took a blood reading (fingerprick) and it came back at 5.7 mmol/ls that is also normal. Your fasting blood sugars are very good at 4.4 to 4.8 - great! If I'm reading you right, you want to know why your numbers have come down? Insulin resistance is usually the reason why one's blood sugars rise above 6.0% which in most countries (excluding the US which uses 5.7%) is the point at which you are classed as prediabetes. Insulin resistance means your body doesn't use insulin effectively causing blood sugars to stay in the blood stream instead of being utilized by your cells for energy. It may be because you have become more sensitive to insulin. Insulin resistance can rise and fall in both none diabetics and diabetics a like. Did you change your diet, or did you increase exercise ? In any event, congratulations!
Edited to add prediabetes