If you can at least get a course of the initial loading doses then you may see some kind of improvement and it may convince you, if not the medics, that this is the problem.
But, usually with this illness you have a weird kind of low mood, you find it difficult to be assertive, so it's really better if someone else can look at the information and fight on your behalf.
After all, it's only a vitamin - what have you got to lose by pushing for it?
It's not going to cause you more harm, and you can have it while you're waiting for whatever referrals or tests they want to send you for.
How do I know about it?
I was ill. I had blood tests. They said there was nothing wrong with me. Every symptom I had they put down to being psychological - to the point of ridiculous. My hair was falling out, I was losing my sight, I couldn't lift my arms up, I was falling over, I was bruising all the time.
Turns out my very low b12 had been identified one of the first times I went to the doc. But nobody did anything about it.
Even then, when it was picked up much, much later, they still did next to nothing. I researched, treated myself and reversed the problem.
No, I'm not right, but I'm not dead either. Which is good.
Long term damage results in axonal death - the nerves die - so picking up on it early is very important.
I'm truly amazed at how many people on here appear to be very symptomatic and b12 is not being identified or treated appropriately when it is.
You can give b12 simply to see what happens. It's not toxic, you can't overdose and it's cheap - what have the medical profession got to lose?