I suspect that your low levels of these two vitamins are not related.

Low vitamin D levels are very common in people of all ages. Vitamin D is primarily made in the skin when it is exposed to sunlight. Few natural foods contain vitamin D. So if you are not drinking liquids (like milk) or eating foods (like cereal) with added vitamin D and you avoid the sun, it’s no surprise that your vitamin D level would be low.

The low level of B12 could indicate an underlying disorder. But first you need to look at your diet.

Even though you call your diet normal, you might not be getting enough vitamin B12 from your choice of foods. You might not be a meat eater. Meats, especially liver, are rich in B12. Vegetarians are prone to B12 deficiency. But many people who avoid meat don’t become deficient in vitamin B12. Many other foods, especially fish, contain vitamin B12.

There are a couple of diseases that could cause low levels of vitamins D and B12. Celiac disease (gluten sensitivity) might cause vitamin and mineral deficiencies without specific symptoms. Crohn’s disease could also cause both, but most people with Crohn’s will have symptoms such as abdominal pain and frequent stools.

Tell your doctor about any symptoms you might be having. Then ask for recommendations regarding vitamin supplements. The doses of the supplements will depend upon your specific test results.