Vitamin D vs B12 - what's the difference?
Both are commonly deficient, but they do different jobs: vitamin D is for bones and immunity, B12 for blood and nerves. Here's the breakdown.
Vitamin D
Affects calcium absorption, bones and immunity. Made in the skin from sunlight; deficiency is very common.
Vitamin B12
Needed for blood production and the nervous system. Comes from animal foods; deficiency is common in vegans and older adults.
Key differences
- Vitamin D is bones/immunity; B12 is blood/nerves.
- D depends on sunlight; B12 on diet (animal foods).
- B12 deficiency can cause anemia and neurological signs; D - fatigue, bone issues.
- They're different tests; often checked together in a vitamin panel.
Bottom line
Different vitamins, different roles - not interchangeable. For fatigue or a restricted diet, your doctor may check both.
Frequently asked questions
Can I check both at once?
Yes - they're often in the same vitamin panel, along with folate.
Which is more commonly deficient?
Vitamin D is very common (little sun); B12 especially in vegans and older adults.
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