With so many vitamins and minerals out there, it’s hard to know if you’re meeting the daily-recommended amounts of each. Vitamin B12 is one nutrient many people are lacking in their diet. Unlike vitamin D and vitamin K, your body doesn’t make its own vitamin B12, so you have to get it from the food you eat to get it at all.

How can you know if you’re getting enough vitamin B12, and if you’re deficient, what’s the best treatment? You’re about to find out.