B12 is a water soluble vitamin so there is no fear over dose. We can start suplimenting it without test too. Btw insted of starting any medication randomly there is a need of proper discussion about your illness .with detailed history of your complains and past medication
Next Steps
take an apointnet with a doctor and tell in details about Your past history / medications / illnesses / habbits etc.
Health Tips
take more of miIk egg and Animal source food