If you are getting the synthetic cyanocobalamin form, and you are genetically one of those people who cannot activate it into its methyl form, you will not see any improvements from cyano injections.

This is a common mutation, and can be tested for... MTHFR polymorphisms. You can also get an MMA test which will show if the B12 in your injections is working. Low MMA results demonstrate good conversion.

Here is my B12 thread. It is pretty long:
http://neurotalk.psychcentral.com/thread85103.html

You can get very good results with oral 5mg methylcobalamin (B12) daily taken on an empty stomach. Within 3 months you should show higher levels.

This link explains the medical issues:
http://www.aafp.org/afp/2003/0301/p979.html

And this link explains MTHFR failures:
http://mthfr.net/

Methylcobalamin is available online... iherb.com will ship to UK and other countries.

The drug you take has caused neuropathy in some patients...allopurinol. You might consider getting off this drug. It has a long list of other side effects too.