B12 at 503, should I supplement with more than B complex?

I know 503 is technically not deficient, but it's not optimal either. The last time I had my B12 tested was about a year and a half ago and it was at 616.

I've been suffering with gastritis and esophagitis for the past 3 months and it has really messed up my eating habits. I used to eat very clean and healthy but for the past 3 months I've been eating a bland diet. More recently my appetite has come back full force, but with that I've gotten very dizzy over the past 2 weeks and I'm wondering if this could be why.

I started taking a b complex again about a week ago and I'm wondering if I could benefit from supplementing more aggressively to get my levels back up.