can b12 injections cause itchy skin What happens if you inject wrong? Benefits of Vitamin B12 Injections What Happens When You're Allergic

High-dose oral B12 can even help overcome mild absorption problems, as some of the vitamin is absorbed passively

After that initial period, it is common to continue injections monthly, though less frequent intervals might be OK if cobalamin blood levels are supportive

[7] [9] Patients with a history of oxalate nephrolithiasis (kidney stones) or hyperoxaluria should avoid high-dose vitamin C administration, as ascorbic acid is metabolized to oxalate, which may precipitate stone formation or exacerbate renal impairment

Wallace, Natasha (2013-08-02)

Oral absorption is poor and first-pass metabolism heavy, so both routes land in roughly the same place

[7] [9] Use is also contraindicated in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency, as high doses of ascorbic acid may induce hemolysis in this population