Print OverviewMyalgic encephalomyelitis/chronic fatigue syndrome, also called ME/CFS, is a complicated condition. It causes extreme fatigue that lasts for at least six months. Symptoms worsen with physical or mental activity but don't fully improve with rest. The cause of ME/CFS is unknown, although there are many theories. Experts believe it might be triggered by a combination of factors. There's no single test to confirm a diagnosis. You may need a variety of medical tests to rule out other health conditions that have similar symptoms. Treatment for ME/CFS focuses on easing symptoms. SymptomsSymptoms of ME/CFS can vary from person to person, and the severity of symptoms can fluctuate from day to day. In addition to fatigue, symptoms may include: Extreme exhaustion after physical exercise or mental activity. Difficulty with memory or thinking skills. Dizziness that gets worse when moving from lying down or sitting to standing. Muscle or joint pain. Unrefreshing sleep. Some people with this condition have headaches, sore throats, and tender lymph nodes in the neck or armpits. People with the condition also may become extra sensitive to light, sound, smells, food and medicines. When to see a doctorFatigue can be a symptom of many illnesses. See your healthcare professional if you have persistent or excessive fatigue. Request an appointment There is a problem with information submitted for this request. Review/update the information highlighted below and resubmit the form. From Mayo Clinic to your inbox Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. Click here for an email preview. Email Address 1 ErrorEmail field is required ErrorInclude a valid email address Learn more about Mayo Clinic’s use of data. We use the data you provide to deliver you the content you requested. To provide you with the most relevant and helpful information, we may combine your email and website data with other information we have about you. If you are a Mayo Clinic patient, we will only use your protected health information as outlined in our Notice of Privacy Practices. You may opt out of email communications at any time by clicking on the unsubscribe link in the email. Subscribe! Thank you for subscribing! You'll soon start receiving the latest Mayo Clinic health information you requested in your inbox. Sorry something went wrong with your subscription Please, try again in a couple of minutes Retry CausesThe cause of myalgic encephalomyelitis/chronic fatigue syndrome, also called ME/CFS, is still unknown. A combination of factors may be involved, including: Genetics. ME/CFS appears to run in some families. Some people may be born with a higher likelihood of developing the condition. Infections. Some people develop ME/CFS symptoms after they recover from a viral or bacterial infection. Physical or emotional trauma. Some people report that they experienced an injury, surgery or significant emotional stress shortly before their symptoms began. Energy use. Some people with ME/CFS have difficulty converting fats and sugars, which give the body fuel, into energy. Risk factorsFactors that may increase your risk of myalgic encephalomyelitis/chronic fatigue syndrome include: Age. ME/CFS can occur at any age, but it most commonly affects young to middle-aged adults. Sex. Women are diagnosed with ME/CFS much more often than men. It may be that women are more likely to report their symptoms to a healthcare professional. Other medical conditions. People who have a history of other complex medical conditions, such as fibromyalgia or postural orthostatic tachycardia syndrome, may be more likely to develop ME/CFS. ComplicationsSymptoms of ME/CFS can come and go. They often are triggered by physical activity or emotional stress. This can make it difficult for people to maintain a regular work schedule or to even take care of themselves at home. Many people may be too weak to get out of bed at different points during their illness. Some may need to use a wheelchair. By Mayo Clinic Staff Request an appointment Diagnosis & treatment Jan. 17, 2026 PrintShow references Kellerman RD, et al. Myalgic encephalomyelitis/Chronic fatigue syndrome. In: Conn's Current Therapy 2025. Elsevier; 2025. https://www.clinicalkey.com. Accessed May 1, 2025. Gluckman SJ. Clinical features and diagnosis of myalgic encephalomyelitis/chronic fatigue syndrome. https://www.uptodate.com/contents/search. Accessed May 1, 2025. Ferri FF. Chronic fatigue syndrome. In: Ferri's Clinical Advisor 2025. Elsevier; 2025. https://www.clinicalkey.com. Accessed May 1, 2025. Myalgic encephalomyelitis/chronic fatigue syndrome. U.S. Centers for Disease Control and Prevention. https://www.cdc.gov/me-cfs/hcp/clinical-overview/index.html. Accessed May 1, 2025. Chronic fatigue syndrome. Merck Manual Professional Version. https://www.merckmanuals.com/professional/special-subjects/chronic-fatigue-syndrome/chronic-fatigue-syndrome. Accessed May 1, 2025. Goldman L, et al., eds. Fibromyalgia. In: Goldman-Cecil Medicine. 27th ed. Elsevier; 2024. https://www.clinicalkey.com. Accessed May 1, 2025. Gluckman SJ. Treatment of myalgic encephalomyelitis/chronic fatigue syndrome. https://www.uptodate.com/contents/search. Accessed May 1, 2025. Bateman L, et al. Myalgic encephalomyelitis/Chronic fatigue syndrome: Essentials of diagnosis and management. Mayo Clinic Proceedings. 2021. doi.org/10.1016/j.mayocp.2021.07.004. AskMayoExpert. Chronic fatigue. Mayo Clinic; 2023. Medical review (expert opinion). Mayo Clinic. Dec. 19, 2022. 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There is a problem with information submitted for this request. Review/update the information highlighted below and resubmit the form. From Mayo Clinic to your inbox Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. Click here for an email preview. Email Address 1 ErrorEmail field is required ErrorInclude a valid email address Learn more about Mayo Clinic’s use of data. We use the data you provide to deliver you the content you requested. To provide you with the most relevant and helpful information, we may combine your email and website data with other information we have about you. If you are a Mayo Clinic patient, we will only use your protected health information as outlined in our Notice of Privacy Practices. You may opt out of email communications at any time by clicking on the unsubscribe link in the email. Subscribe! Thank you for subscribing! You'll soon start receiving the latest Mayo Clinic health information you requested in your inbox. Sorry something went wrong with your subscription Please, try again in a couple of minutes Retry