I also take acid reflux medication

Plaquenil can definitely cause upset stomach. When I first started on hydroxychloroquine, I was taking ranitidine (zantac) twice a day as an antihistamine, and it largely stopped that side effect. Since zantac is no longer on the market, I take famotidine (pepcid), and it works for any upset stomachnissues as well.

Taking it after eating with at least 8 oz of water and staying upright for a couple of hours may help.

Glad I can give some insight

Thanks for that I think it's I've just started hydroxychloroquine and its that