Numbness in feet

A fellow yogi in my seniors class says her toes are going numb during the day and more so at night. She has sciatica on one side. What do you think? (Both feet are going numb.)

Is it all the toes that are going numb? There is a chart revealing the pathways of nerves called dermatomes. By looking at the chart one can determine the specific nerve root causing the numbness. The Sciatic has four nerve roots in the sacral and lumbar regions. Is it possible that the compression has progressed to the other side a sign she needs more water. Water is lost during day so that the discs are fuller in am hence less symptoms.