Once a week I experience belching with gas, rotten egg taste followed by diarrhea over the next 12 to 24 hours. I first thought that it was do to methotrexate, but I stopped the methotrexate for 2 weeks and I still had symptoms, although not nearly as bad, I take the mtx on Friday each week for rheumatoid arthritis. When I stopped it seemed like I could eat anything at all during the week but I still had symptoms on Saturday or Sunday. I stopped taking Benefiber and Metamucil several months ago. I stop taking any over the counter vitamins. I take hctz 25mg and folic acid 1 mg every morning. This Friday I plan to resume the mtx therapy. I had been taking mtx 2.5 mg 5 tablets every Friday for the past 3 & 1/ years. This Friday when I start again I will try 2 tablets, the next Friday I will go to 3 tablets. I am 75 yrs old. Perhaps my body does not eliminate the mtx as well as it did 3 years ago. At different times I had thought that the symptoms were due to lactose intolerance, but I can drink milk and eat ice cream during the week. I do have some small stones in my gall bladder that have not caused any problems as far as I know. When my Urologist wanted me to try taking Flomax 0.4 mg daily, I would start on Saturday night, next dose on Sunday morning, next dose on Monday morning. By that time I started to experience diarrhea and vomiting lasted almost constantly for 3 hours and then continued for 12 to 24 hours. I tried to take the flomax for 3 weeks in a row and the same thing happened every time. I discussed this with the rheumatologist and he did not think that it was due to methotrexate. I have not lost weight. In the past year my waistline has increased about 3 inches. What tests should I ask my primary care doctor to run. Should he check creatinine clearance? . Is there any way to check to see if I am getting too high a blood level of methotrexate? It does not seem to matter what I eliminate from my diet, I still am having symptoms on the weekends. I do not drink alcoholic beverages. I do not use any medication that has not been prescribed by my doctor. I do not take herbal products. I do not take any OTC fiber products.