This Vitamin Deficiency May Be The Reason You’re Always Tired
Key takeaways
- Even if you're sleeping well, feeling completely worn out often may be a sign that something else is going on.
- There's a good chance this feeling is connected to low vitamin D levels.
- Low energy or occasional fatigue is a common complaint of vitamin D deficiency, which is also alarmingly widespread.
Why this matters: practical guidance grounded in recent research or expert insight.
Author: Molly Knudsen, M.S., RDNMay 01, 2026Registered Dietitian Nutritionist By Molly Knudsen, M.S., RDNRegistered Dietitian Nutritionist Molly Knudsen, M.S., RDN is a Registered Dietician Nutritionist with a bachelor’s degree in nutrition from Texas Christian University and a master’s in nutrition interventions, communication, and behavior change from Tufts University. She lives in Newport Beach, California, and enjoys connecting people to the food they eat and how it influences health and wellbeing.Image by jamie grill atlas / StocksyMay 01, 2026You know that feeling when crawling out of bed feels too much like an effort or lifting your hairbrush seems like a full workout? Even if you're sleeping well, feeling completely worn out often may be a sign that something else is going on.
There's a good chance this feeling is connected to low vitamin D levels.
Low energy or occasional fatigue is a common complaint of vitamin D deficiency, which is also alarmingly widespread. About 29% of U.S. adults1 are deficient in vitamin D (aka have blood levels less than 20 ng/mL, and 41% of adults1 have insufficient vitamin D levels (less than 30 ng/mL).