Ttc post methotrexate

We're not trying right now, but wanting to know if anyone started taking folic acid post methotrexate before there level was 0? I know they say not too until your level is 0, but not sure how bad it would be considering my beta hcg is 13 today (one dose of mtx given on sept 10th) and I want to start building up my folic acid as soon as I can so I'm nice and healthy for when we do start trying again around Christmas.. Any info would be great! :) thanks!