Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Stop using Metamucil and call your doctor at once if you have:
constipation that lasts longer than 7 days;
rectal bleeding; or
severe stomach pain.
Common side effects may include:
bloating; or
minor change in your bowel habits.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Metamucil side effects (more detail)
