I was diagnosed with low b12 (147) after suffering from neuropathy. dr prescribed injections over 5 days. how long will it take to see improvement?

Vitamin B12...: Vitamin B12 is a water soluble vitamin, and excess of the vitamin is excreted in the urine. It requires other factors in the body for proper absorption. Significant measurable effects , provided no other factors limiting it's proper metabolism, are typically seen after one month of treatment. (Reference:http://dx.doi.org/10.1155/2014/921616)