Rapid weight loss in a few days?

I’ve only started on Mounjaro since last Wednesday-so 5 days and I’ve done a weigh in today and according to my scales, I’ve lost 12 lbs? Surely not? My joggers are falling down on me I have to admit as I seem to be losing it from my stomach. I’m following a healthy diet and drinking lots of fluid so I’m trying to diet the correct way?