When is the best time of day to take V B12 sublingually?

When is the best time of day to take V B12 sublingually? I started taking V B12 sublingually because my B12 was very low (220). I seemed to have energy again. But then after about a month, it seems like I'm back to feeling how I was feeling. Yet, I am still taking the Vitamin B12 (and Vitamin D - also deficient - 17). I'm wondering if perhaps my problem is that I have not been taking the Vitamin B12 and Vitamin D at the same time every day. Lately, I have taken them at night. Perhaps that is the problem? I will try to remember to take in morning and see if that brings me back to how I was feeling (i.e., more energized). Meanwhile, I thought I would ask this question.