Changing my stack from Tirz + Reta to…

Sema side effects hit hard. I kept ginger beer around constantly to handle the nausea, and that was still needed after nine months on it.

The GIP action in tirz is said to reduce its GLP-1 side effects, which is why it is usually better tolerated than sema. Reta shares that GIP activity, so adding sema to reta might give a more focused GLP-1 increase without as many issues as sema by itself. It seems worth trying slowly and carefully. I keep some sema around for exactly that possibility if it ever comes up, since it stores well long-term in the freezer and could be useful as a backup later.

I began with tirz, hit a plateau at the higher weekly dose for a couple months, then added reta on top. Now I run a lower tirz amount with reta at 10 mg and the scale is still moving, though slowly. Other people report bigger drops on similar combinations, but I feel much better overall than I did a year ago. I have avoided sema because everyone I know personally who used it dealt with bad GI problems.

I am planning 3 mg reta tonight and then 1 mg tirz on Sunday, followed by 4 mg reta the next Wednesday. Has anyone had success with a schedule like that?

There is a reason not to. Published numbers on how strongly each drug binds the different receptors are inconsistent because results vary by assay method and whether the molecule was albumin-bound during testing. Most of the detailed data appears only in the original development papers. After reviewing those, tirzepatide actually shows the strongest GIP activity, not reta, and that is likely why tirz produces fewer side effects relative to its weight-loss effect. If reta truly had stronger GIP action it should cause even fewer GI problems, yet it does not. Semaglutide is stronger at GLP-1 receptors, but tirz and reta are dosed higher, which narrows the gap, and tirz acts as a biased agonist at GLP-1.