Why might someone feel tired with no energy all the time and what can be done?

Reviewed by Yoshinori Abe, MD

Internal Medicine

Persistent fatigue, or feeling tired all the time, can stem from several underlying causes, including depression, thyroid disorders (such as hypothyroidism), neurological conditions, anemia, sleep disorders, or vitamin deficiencies like low B12, iron, or vitamin D. Identifying and treating the root cause is essential to restoring healthy energy levels.

Because fatigue has so many possible causes—ranging from easily correctable nutrient gaps to more serious medical conditions—guessing can delay the relief you need. A quick, structured assessment of your symptoms can help you narrow down likely explanations and decide whether self-care, lab tests, or a doctor's visit should be your next step. Take a free, instant, online symptom check to better understand what may be driving your fatigue and confidently plan what to do next.

Reviewed for medical accuracy: 07/14/2026

Important Next Steps

Learn why your tiredness may need care Discover likely causes of persistent fatigue See if fatigue could signal illness Find OTC options for low energy Find a doctor for fatigue causes Understand home remedies for tiredness Check if fatigue needs medical attention

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Explanation

Feeling tired all the time can be very common and might have different causes. Here are some possible reasons:

Depression: People with depression often feel very tired and sleepy. It can affect how they feel and make them not want to do things they used to enjoy. If you think this might be your situation, you can learn more about getting help at 988lifeline.org.
Neurological Issues: Sometimes, problems with the brain and nerves can make a person feel tired during the day. These issues need a doctor's help to find out what's going on and how to fix it.
Vitamin B12 Deficiency: Not having enough vitamin B12 can make you feel very sleepy and tired. This vitamin is important for keeping your nerves and blood cells healthy. If you think you might not be getting enough, a doctor can check your levels and suggest what to do next.

If you're feeling tired all the time, it's a good idea to use a free symptom checker to help identify what might be causing your fatigue and determine the best next steps for feeling better.

(References)

Baldwin DS, & Papakostas GI. (2006). Symptoms of fatigue and sleepiness in major depressive .... The Journal of clinical psychiatry, 16848671.
Maestri M, Romigi A, Schirru A, Fabbrini M, Gori S, Bonuccelli U, & Bonanni E. (2020). Excessive daytime sleepiness and fatigue in neurological .... Sleep & breathing = Schlaf & Atmung, 31444679.
Khawaja I, Yingling K, Bukamur H, & Abusnina W. (2019). Vitamin B12 Deficiency: A Rare Cause of Excessive .... Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine, 31538608.

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