Fatigue, a common problem among people living with HIV, refers to overwhelming tiredness, exhaustion or lack of energy. Most people experience temporary tiredness, but fatigue goes beyond just feeling sleepy. Some people develop severe or chronic fatigue that can interfere with daily activities. What’s more, fatigue is often accompanied by physical weakness and cognitive problems known as “brain fog.”

Many health conditions and lifestyle factors can lead to fatigue, including the following:

Inadequate sleep. Most adults need at least seven hours of sleep a night. Inadequate sleep—for example, due to an overly busy schedule or sleep disturbances, such as insomnia or sleep apnea—can lead to ongoing fatigue. Stress, chronic pain, certain medications, substance use and inadequate exercise can all contribute to poor sleep.

Psychological causes. Anxiety and depression are often associated with fatigue and lack of energy. Depression can also lead to apathy and reduced motivation.

Anemia. Anemia occurs when red blood cells don’t carry enough oxygen. This can happen when blood is lost, the body doesn’t produce enough red blood cells, these cells are destroyed too quickly or they don’t make enough hemoglobin, the protein that transports oxygen. Causes include inadequate iron, inherited conditions, infections and medications that deplete blood cells.

Nutritional deficiencies. In addition to inadequate iron, low levels of other nutrients, including vitamin B9 (folate), vitamin B12 (cobalamin), vitamin D and certain minerals, can also contribute to fatigue. A balanced diet usually provides adequate nutrition, but some people may need supplements.

Medications and substance use. Many prescription and over-the-counter medications can cause drowsiness. Opioids, benzodiazepines and alcohol can also lead to fatigue. Stimulant drugs and caffeine, which some people use to combat fatigue, can interfere with sleep and make matters worse.

Infections. Fatigue is a common symptom of many infectious diseases, including influenza, hepatitis C and COVID-19. Infections can cause inflammation, and the immune system’s response to pathogens can trigger fatigue.

Other medical conditions. Many people with cancer experience debilitating fatigue, and chemotherapy and radiation can damage the bone marrow and cause anemia. Diabetes, multiple sclerosis, kidney disease, chronic lung disease, autoimmune conditions and congestive heart failure are also associated with fatigue.

Endocrine problems. Low levels of certain hormones can lead to fatigue. These include adrenal insufficiency (inadequate production of cortisol), hypothyroidism (an underactive thyroid gland) and hypogonadism (inadequate production of testosterone or estrogen).

Chronic fatigue syndrome. Also known as myalgic encephalomyelitis or ME/CFS, this condition is characterized by profound fatigue that may worsen after physical or mental activity. The causes of ME/CFS are not well understood, but it sometimes comes on after a viral infection. Some experts think long COVID is related to ME/CFS.

Although fatigue is a common symptom of many physical illnesses, health care providers sometimes too quickly dismiss it as a psychosomatic problem. It’s important to work with your doctor to figure out the causes of fatigue, which is the first step toward managing it.

Treatment for fatigue depends on its specific causes. Many types of fatigue can benefit from medical treatment or lifestyle changes. Stay on antiretroviral therapy to maintain an undetectable viral load. If your HIV meds are causing fatigue or interfering with sleep, ask your doctor about switching them. If you have debilitating fatigue, pace yourself, and devote your limited energy to the most important tasks and the activities you most enjoy.