3-4 grams at once, or throughout the day?
At once with no carbs would cause severe hypoglycemia, but spread out throughout the day (in doses no larger than half a gram at one time) wouldn't cross your eyes. It would probably deepen ketosis, and upregulate the GLUT-4 receptors to grab any protein that was turned to glucose via gluconeogenesis. If you're going to go ahead with this, I suggest you play with your doses to see how much you can take without getting the hypoglycemia hungries...