Seek medical advice if you are taking B12 supplements and experience: Persistent skin changes, particularly acne-like eruptions or rosacea worsening Unexplained headaches or dizziness that coincide with supplement use Gastrointestinal symptoms including nausea or abdominal discomfort Any allergic reactions such as rash or itching Call 999 or go to A&E immediately if you experience: Difficulty breathing Swelling of the face, lips, tongue or throat Severe rash or itching Other symptoms of severe allergic reaction after taking B12 These symptoms warrant review of your supplementation regimen
Kaszs N, Budai M, Budai L, Grf P, Zimmer A, Klebovich I
J Comp Neurol 484(4):403417
XieHZhouFLiuLZhuGLiQLiCet al
Although it is not confirmed in humans, its recommended to avoid in patients with a personal or family history of medullary thyroid carcinoma or those who have Multiple Endocrine Neoplasia syndrome type 2
Chronic gastritis is a persistent condition that may resolve