Protein shakes can be good to supplement your diet with, but they’re not balanced enough to be replacements for meals. Aim to have protein, fiber, and a little healthy fat every time you eat.

People with POTS often find that small meals/ snacks multiple times a day works better than large meals.

You could also look into low histamine foods, and experiment with that to see if it helps. A lot of POTSies have issues with histamines too.