Additionally, since keto can be harmful to a fetus, the keto diet should be avoided during pregnancy. “Also, ketones are harmful to patients who cannot correct the metabolic acidosis caused by them, ie, those with liver, kidney, or pulmonary disease,” Dr. Gonzalez-Campos adds.Of course, not all protein powders are low in carbohydrates, so you'll have to check the label. Israetel recommends a powder that contains casein protein, which is digested slowly to help you stay full longer. Or, you could try a protein powder formulated to be nearly carb-free for keto dieters. According to Israetel, the fake sugars won't knock you out of ketosis.