Its a small yellow lill blank on one side and has M and score mark with 1 under it. please help, found it and dont know what it is and cant find any info. Thanks!! ## A yellow, round, scored tablet imprinted with "M 1" on one side and blank on the other, is identified as Rheumatrex (Methotrexate) 2.5mg. NOTE: you can also view a photo of the pill by running a search on google images for "yellow pill M 1". Methotrexate is noted to be used in the treatment of certain types of cancer, severe psoriasis, and rheumatoid arthritis. Learn More: Methotrexate Details I hope this helps! :)