I haven’t seen any data or any studies on the dose/response relationship for GFJ on sirolimus levels. Its a good question - I just don’t know the answer. The best way to find out is do the test yourself with blood tests afterwards each time.
The other much less accurate approach is by “feel” or side effects. Perhaps @Agetron or @DeStrider have some thoughts or experiences with this approach, or even some opinions based on their blood test results?
In the original study that got everyone interested in this GFJ approach they did mention this:
Although the magnitude of the interaction is highly variable, it is reproducible within individuals and seems to be dependent on small bowel CYP3A4 content, i.e. persons with the highest intestinal CYP3A4 content have the largest reduction in enzyme levels and subsequently the greatest effect on drug metabolism
This suggests to me that there likely is a positive dose response relationship, but it will likely vary by person. So - I would guess that more grapefruit (or juice) up to some point may increase the AUC for the rapamycin.