Get B12 from fortified foods or supplements after 50
Added
NIH says many older adults don't make enough stomach acid to absorb the B12 naturally found in food, so people over 50 should get most of it from fortified foods or supplements. If you log macros, check B12 too, and ask your doctor about a blood test if you take acid reducers like omeprazole or the diabetes drug metformin, which can lower B12.
The result
Result: NIH Office of Dietary Supplements: adults need 2.4 mcg a day, and B12 deficiency affects between 3% and 43% of older adults.
Note: Not medical advice. Talk to your doctor or pharmacist before starting any supplement, especially if you take medications.
Source
NIH Office of Dietary Supplements: Vitamin B12 Fact Sheet for Consumers (opens the original source in a new tab). Check it for the latest numbers before you act.