red urine after b12 injection is from Does a B12 shot change urine color to pinkish? Vitamin B12 Injection: Energy Boost

This lifelong therapy rapidly corrects deficiency, restores red blood cell production, and protects nerve function

[152] Healthcare practitioners at clinics and spas prescribe versions of these intravenous combination products, but also intramuscular injections of just vitamin B 12

Support Your Mental Well-being and Cognitive Function: Vitamin B12 is essential for synthesizing mood-regulating chemicals, serotonin and dopamine

For example, Trp is the necessary precursor for the de novo NAD + biosynthetic pathway (also known as the kynurenine pathway)

This is the first step in another adenosine production pathway, which typically includes CD39 catalyzing adenosine triphosphate (ATP) to produce adenosine monophosphate (AMP)