I Have Done A Liver Function Test Before I Start

I have done a liver function test before I start using methotrexate as advices by the doctor . All came good except ALT came out 52 slightly higher than range 0-52 . Can I still take methotrexate which is known for elevating the ALT levels further ? At which level Should I stop it if elevated ? If it's a fatty liver would this stop me from taking it ?

NB: I checked for heptatitis B & C ( negative )