If you take a daily B12 supplement or multivitamin and your levels are mildly elevated (900 to 1,200 pg/mL), the most likely explanation is the supplement
Not intended for human or veterinary use, diagnosis, treatment, or consumption
Supplement Facts: Serving Size: 30g Servings Per Container: 5 Amount Per Serving: Energy kcal: 114 kcal Energy kJ: 486 kJ Fat: 0.54g of which saturates: 0.24g Carbohydrates: 0.66g of which sugars: 0g Fibre: 0.20g Protein: 27.72g Salt: 1.02g *RI - Reference Intake Ingredients: Blue Raspberry: Beef Protein Isolate (92%), Citric Acid, Xanthan Gum (Thickener), Natural Flavour, Sucralose (Sweetener), Colour (Brilliant Blue E133*)
[4] In a further step, some NAD + is converted into NADP + by NAD + kinase, which phosphorylates NAD +
This cold-chain requirement adds substantial cost, limits distribution to pharmacies with adequate cold storage capacity, and creates logistical challenges in resource-limited settings and during natural disasters or supply chain disruptions