You can take it with or without food. Senna takes about 8 hours to work. It's usual to take it at bedtime so it works overnight. Drink plenty of fluids (6 to 8 glasses a day) while you're taking senna or your constipation may get worse.

If you are taking certain senna products (Ex-Lax regular ormaximum strength tablets or Perdiem Overnight Relief), swallow the pills whole with a glass of water; do not split, chew, or crush them.