While this is a good level, it remains that if you cannot methylate you will show a level in the blood that is not working.
The methylation failure (methylation activates B12) is fairly common. 10-30% in US have some mutations in this system.
Using methylcobalamin bypasses these errors.

Also if you do not have the carrier proteins (transcobalamins) the movement of B12 into tissues may be impaired. (this is in the video).

So doing the collateral testing of MMA and homocysteine may be informative. MMA shows if the B12 you have is working. A high MMA reading suggests that B12 is not working properly.

Metformin is known to impair B12 absorption in those taking it.

Since low B12 damage occurs in the spinal cord (as well as in the brain), back symptoms could be compression (mechanical) or nerve related in the cord (low B12 resulting in myelin damage).

Diabetics also lose magnesium in the urine. The reasons for this are not well understood, but it has been demonstrated in studies. So making sure you eat foods that provide the magnesium you need daily, is very important. Low magnesium would impair nerves and muscles, and many other functions which require it in the body. Some drugs like diuretics, caffeine and alcohol also deplete magnesium. Acid blocking drugs for heartburn and GERD block its absorption from food.

Many of our PN posters find improvements by paying attention to magnesium.