This Common Vitamin Deficiency Could Be the Reason You’re Always Tired, Experts Warn

By Beth Ann Mayer, Dec 2, 2025

Yes, vitamin B12 deficiency could be a reason you’re always tired. However, that blood test might reveal you aren’t vitamin B12 deficient, which is why it’s crucial to get one rather than self-diagnose. “It’s important to realize that most people living in the modern world are not vitamin deficient, with the exception of certain groups,” states Dr. Alex Dimitriu, MD, a double board-certified psychiatrist and sleep medicine specialist and the founder of Menlo Park Psychiatry & Sleep Medicine. Yet even people who are more at risk for a B12 deficiency have a less than 5% chance of having one. For instance, only about 3.7% of people ages 60+ are vitamin B12 deficient (or having serum vitamin B12 levels below 200 picograms per milliliter). Real talk: “In my work as a sleep specialist, the most likely explanation for most of us who feel fatigue is too much stress or not enough sleep—not necessarily a vitamin deficiency,” Dr. Dimitriu explains.

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