Can you get dependent on your Vitamin B12 injections?

Some people report that once they have started on the B12 injections (which makes them feel much better), when they stop they feel absolutely terrible - get all the symptoms worse.

Why does this happen?

I wonder if there's some other "factor" we don't know about.  We know that the body stores can change without changing the blood level, exactly the same as in a car.  If you compare it to the engine oil in a car, the oil pump pumps the oil up to a certain pressure (same as blood serum concentration of B12) almost regardless of the level of stores of B12 in the body.

Then when the body stores get below a certain point, the blood serum B12 begins to fall.  If we stick with the car engine analogy, this is when the oil light comes on - highlighting that there is a problem.

But the oil in the sump can continue to fall, and you only get symptoms (in the car - that awful crunching sound; in the body - neuropathy, immune problems etc) once the oil (B12) level gets so low that it is dangerous.  And then if you don't take action when you get the symptoms, it just gets worse and worse and worse.

When you have B12 replacement therapy, it should renew the body stores

Unfortunately we don't know much about this.  Obviously if you inject B12 into the blood, there is going to be lots more B12 in the blood.  So the symptoms go away.  But does something underlying in the body continue to deteriorate, which means that when the B12 isn't there, you get the symptoms you would have got if you hadn't had B12 supplements?  I mean that if you notice a tingling in your leg, and usually this would develop into paralysis after 6 months, does it sort-of develop into paralysis only your leg functions normally just as long as you keep taking B12 supplements?  So that when you stop taking the supplements, you don't go back to where you were before, you go to where you WOULD HAVE BEEN.

To tell the truth i don't know how this works or whether it works like this, but the dotted line in the graph above shows the underlying deteriorating condition, whereas the green line shows blood serum level and you avoid any of the symptoms by getting your B12 injections.

Comments gratefully received