@Orangesandlemons77 having just come out of hospital after suffering an inflamed gallbladder this question is close to my heart. It's so good you're thinking about this.
I've never had any issues with my gallbladder before so this was a shock to go through.
I worry the gallbladder isn't being talked about enough by MJ providers. It's not at all uncommon to run into problems with fast weight loss. I've been losing at a rate of 1.8lbs a week (which isn't even that fast) but I guess a total weight loss of 4.7 stone in seven months does have an impact.
Symptoms to look out for (these were mine at least): severe vomiting, constant pain in the upper centre of the abdomen that does not get better after being sick, pain moving to the upper right of abdomen and radiating to back and shoulder.
Fasting apparently can be bad for the gallbladder as can eating high fat foods. I often skip meals.
Things that help prevent issues: regular small meals, vitamin C, peanut butter, avoid heavily processed foods or greasy food, fibre. Would love to hear more if anyone has ideas.
Ironically being obese can cause gallstones but losing weight can also cause gallstones...damned if you do, damned if you don't.
The Dr at the hospital was keen to stress you need to stay on the lowest effective dose possible for as long as possible. Apparently 12.5mg and 15mg over long periods of time may cause issues (haven't been able to research this yet and I was in such agony at the time I didn't ask many questions).