does sublingual b12 work as well as injections Best Vitamin Injection Site: Administering B12 Shots Do Oral B12 Pills Work

Within 48 hours after injection of 100 or 1,000 mcg of vitamin B12, 50 to 98% of the injected dose may appear in the urine

Older people and people with digestive tract conditions are most at-risk for developing vitamin B12 deficiencies

This can show up as symptoms such as delayed growth and development (failure to thrive), regression in neuromotor skills (such as losing the ability to roll over or grasp objects), failure to maintain eye contact (even in an infant who previous could do so), general muscle weakness, lethargy, excessive sleepiness, feeding difficulties, and even brain shrinkage

But, how well it works depends on how well the body absorbs it

Alternatively, 1000mcg can be given daily SC/IM for 2-7 days, followed by maintenance treatment