Most of the time fatigue can be traced to one or more lifestyle issues, such as poor sleep habits or lack of exercise. Fatigue can be caused by a medicine or linked to depression. Sometimes fatigue is a symptom of an illness that needs treatment.

Lifestyle factors

Fatigue may be related to:

1. Alcohol or drug use
2. Eating poorly
3. Medicines, such as ones used to treat allergies or coughs
4. Not enough sleep
5. Too little physical activity
6. Too much physical activity

Conditions

Exhaustion that doesn't let up might be a sign of:

1. Adrenal insufficiency
2. Amyotrophic lateral sclerosis (ALS)
3. Anemia
4. Anxiety disorders
5. Cancer
6. Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)
7. Chronic infection or inflammation
8. Chronic kidney disease
9. COPD — a long-term lung disease that causes trouble with breathing.
10. Coronavirus disease 2019 (COVID-19)
11. Depression (major depressive disorder)
12. Diabetes
13. Fibromyalgia
14. Grief
15. Heart disease
16. Heart failure — a condition in which the heart doesn't pump blood as well as it should.
17. Hepatitis A
18. Hepatitis B
19. Hepatitis C
20. HIV/AIDS
21. Hyperthyroidism (overactive thyroid)
22. Hypothyroidism (underactive thyroid)
23. Inflammatory bowel disease (IBD)
24. Liver disease
25. Low vitamin D
26. Lupus
27. Medicines and treatments, such as chemotherapy, radiation therapy, pain medicines, heart medicines and antidepressants
28. Mononucleosis
29. Multiple sclerosis
30. Obesity
31. Parkinson's disease
32. Physical or emotional abuse
33. Polymyalgia rheumatica
34. Pregnancy
35. Rheumatoid arthritis
36. Sleep apnea — a condition in which breathing stops and starts many times during sleep.
37. Stress.
38. Traumatic brain injury