Yes it is possible. A blood test is only a window of information for that one day.

If you had dropped from a higher value and are on the way down further...it will not show that.

The body tends to react severely to "drops" depending on how high it was before.

Glucose is the same way. If a person drops 50pts... from 150 to 100 in minutes...they will feel it differently than if the drop is
gradual over hours/days.

I think B12 is the same. Dr. Snow...in the article I quoted on post #70 believes there are people testing in the 400 range who still need higher levels. take a look at his paper...and he is the expert.

You may also have something else going on.... as well.

For example, muscle issues, cramping,stiffness may reflect low magnesium levels. This can be corrected easily too.

Take the methyl form of B12 (the active form) orally 5mg a day on an empty stomach. In 3 months you should test over 1000. There may be some changes for you in those 3 months. Most methylcobalamin is available online at Amazon, iherb.com, Puritan's pride and Swanson's. Using this form, at pennies a day will show within 3months if this is a problem for you.
Take on empty stomach only. That is the only way to get proper absorption.

The urinary incontinence suggests some spinal thing. So keep an eye on that.

If you read the posts on this thread you will understand more.
You just have to do this homework, to be your own advocate.