Is it safe to consume a nutritional shake after it expires?

The expiration date is usually just an estimated time of expiration. It can be the end of efficacy for the preservative and the like. And since it is just an estimation, I think it is never that accurate. Sometimes, the food go rancid just before the estimated expiration date, and there are also times when the food preparation is already expected to expire but still in good condition.

I think that if it's a sealed package with powdered shake mix in it then it should be more than fine. Most packaged things that we buy are non-perishable and are still good after the dates they are labeled to. Many of them are air-sealed and the dates that are put onto the packages are just recommended dates. I personally would still use it but it's really up to you. I buy expired stuff from a store called the Merchandise Outlet in my town and a lot of their stock is expired. They all still taste as good and are much cheaper. I've eaten plenty of stuff that was past expiration date.

Has it been opened yet? That could make a difference. it still probably is not good. I would taste it. If it tastes bad, throw it out.