@anniewee
My GI did not tell me NOT to take it. I looked it up as it was suggested not to take other stimulant laxatives or bulk forming fiber laxatives with it. Here is what it said,
"You should not take Benefiber or Metamucil (psyllium) at the same time as Linzess without talking to your doctor first, as combining them can increase the risk of diarrhea and potentially make both medications less effective by interfering with absorption or masking symptoms, requiring a separation of doses by at least 2 hours and medical guidance for safe use."
I followed that advice as Linzess caused diarrhea at first and very soft stool once it regulated.
Why would I want it to get back to runny? HA!
If your GI told you to take them together, then by all means do so. I'm not a doc! Good luck to you and hope you find what works for you.