I had one day when I had a burger in a bun and fries, two beers, when I went out with a friend. Only time in 3 months I’ve fell off the keto wagon. I thought it would be a good experiment. My ketones two hours later read 9.95–as high as the scale can read, and the opposite of what I was expecting. With the sudden rush of carbs I expected a zero reading and to be off ketosis. The next morning it was back to 3.3ish which is my normal reading for first thing in the morning.
What meter are you using? If 9.95 is ‘as high as the scale can read’, this does not sound like a meter designed to measure acetone, but a common breathalyzer designed to measure BA (breath alcohol) that by fluke of sensor design can also possibly detect acetone, or more likely isopropanol. A device designed to measure acetone does so in parts per million. The common range of acetone during nutritional ketosis is 5-40 ppm. A device that is designed to measure BA does not reliably measure acetone, if at all.
Think of this. 2 hours after eating a substantial carb-loaded meal your system is likely flooded with glucose and insulin in the process of trying to get it out of the blood. This stops ketosis. So if you are using a device that registers ‘as high as the scale can read’ it’s not measuring ketones.
Some folks want to think a cheap BA breathalyzer can measure acetone accurately. See this. If you read through that thread beyond the initial enthusiasm you will discover that unfortunately t’ain’t so.
Also see my attempt to calibrate a cheap breathalyzer with my Ketonix here.