You are so low in vit B12 that you will need the course of injections to take effect. Don't look at side effects - you don't need to know them. Just allow yourself to know that you are going to feel much better when your B12 is at an optimum level. It is only a hormone after all.
Are you taking Folic Acid as well - the two work together - B12 and Folic Acid.... Hope you soon feel better. I too am on injections and always know when I need another dose - so it would suggest you are not yet optimal....
I myself feel worse the day of or after the injection and usually better one day later. There is a theory that depending on what time of day the injection is given, it will cause one to feel tired or more awake. I believe if it is given earlier in the day it causes more fatigue and the opposite is true. Anyhow, just know that it is NOT an unusual response.
Content on HealthUnlocked does not replace the relationship between you and doctors or other healthcare professionals nor the advice you receive from them.
Never delay seeking advice or dialling emergency services because of something that you have read on HealthUnlocked.