For last 8 months my serum alt levels have come back slightly higher than normal. at moment there 67 but should be below 31. should i be concerned?

Possibly: Your elevation is very mild (<5x reference), but has persisted longer than 6mos, so some further consideration should be given to hepatocellular causes: chronic viral hepatitis; autoimmune hepatitis; celiac disease; wilson's disease; hemachromatosis. However, other causes: alcohol intake, medications, exercise, muscle disease, or fatty liver (in the obese). It may be time to see the doc.