Please don't use acronyms that people might not understand.
'The GI Doc', 'I have GI issues', etc
The first 5 results on
https://www.urbandictionary.com/define.php?term=gi
say that it's either "Government Issue" or "General Infantry". Gastrointestinal isn't even among the results.
Google's first few results are likewise about the military.
Keep in mind that HN is a global community.
https://en.wikipedia.org/wiki/Gastrointestinal_tract
Please don't use acronyms that people might not understand.