Mary, sucralose is the exception to that rule -- it's the sweetener in Splenda. It is made from sugar and is chemically considered a sugar, but the body doesn't metabolize it at all. There are no carbs in liquid sucralose, which is what commercial products such as shakes are sweetened with. That's why shakes usually aren't considered to be "evil" the way the bars are!

I'd wait a couple days and give the shake another try, red. There are so many factors that go into upset stomachs that I wouldn't blame it on the shake until you see it happening in a pattern! Do you use packet Splenda a lot, and have you ever noticed it causing a problem?