It is ideal to know before hand, what you need.

People really low, do better on 5mg a day on an empty stomach, at least in the beginning, until they develop good levels.

Without a test, you just will have to go by how you feel.
You can take the 5mg daily as a starter or twice a week (which would be similar to 1mg daily).

Not all of that is absorbed, you know. Only about 1%. Average tested absorption in a study of 1000mcg a day was about 13mcg absorbed based on blood work. The RDA for adults is 2-4mcg daily.

So in the beginning since you have neuro symptoms, you can take one 5mg a day and see how you feel. Without testing you
have only your response to go by. If you ordered the methylcobalamin form -- improved sleeping may be obvious in the first week, since methylB12 helps the brain make melatonin from serotonin.

It is fortunate that B12 doesn't have toxicity reported anywhere, so we can be liberal with it. It is not even expensive.

Typically I suggest taking 5mg daily for about 3 months, and if you don't get tested, and then retested, and you see no major responses by then, I'd assume you are not deficient. If you are over 50 yrs old, suggestions are to take some B12 daily since older people cannot absorb it well anymore. So by then you can do 1mg daily after your 3 months loading up on 5mg.

Make sure you do this when no food is present so the B12 does not get lost in food and miss its target location in the small intestine.