To avoid injury
when upping your mileage, you need to take it slow and allow your body time to adapt to the increased workload. In general, you can add a mile for every run you do per week, provided you then run at least two weeks at the new level before advancing again. If you run four times a week, for example, you can up your weekly mileage by four miles. Then stay at that higher level for two weeks before adding another four.