can i have b12 injections while pregnant Vitamin B12: Symptoms, Dosage & Toxicity Risks Vitamin B12 Injection Sites: All
Description
Unlike tablets, which have to pass through your digestive system, an injection goes straight into the bloodstream

Annals of Clinical and Laboratory Science, 45(4), 426432

They never interfere
Do not increase dose during weeks 1-2 regardless of lack of visible results