Can Vitamin B12 Cause Diarrhea or Make You Poop More? Performance Lab Vitamin B12 Deficiency: Key Symptoms to Recognize Vitamin B12 is essential for various bodily functions, including red blood cell production and proper nerve function. A deficiency in this vital nutrient can lead B12 Shots: Vitamin B12 Injections Benefits, Uses, Risks Dr. Axe Did you know long term use of PPIs like pantoprazole (Protonix) can cause: B12 deficiency hypomagnesemia calcium malabsorption which can lead to bone fx acute interstitial nephritis