More Energy at 60 than at 30?

Persistent Fatigue Has a Standard Workup Before It Has a Name

Tiredness is one of the most common complaints in American medicine and one of the hardest to pin down, because it describes an experience rather than a measurement. Primary-care guidance handles that problem with a sequence: how long the tiredness has lasted, what comes with it, which medicines are involved, and which few tests come first.

The sequence starts with warning signs, moves through a short list of common contributors, and only after six months reaches the formal criteria for a named chronic illness.

Duration is the first variable in every guideline, and the thresholds are short. Mayo Clinic advises making an appointment when two or more weeks of rest, stress reduction, good nutrition and adequate fluids have not relieved fatigue.

A 2023 review in American Family Physician sets the longer marker. "Fatigue lasting six months or longer is considered chronic," it states, and it reports that fatigue is among the top 10 reasons for a primary-care visit, raised by 5% to 10% of patients in that setting.

The 2024 National Health Interview Survey asked adults how often they had felt very tired or exhausted in the past three months. Frequent fatigue, meaning most days or every day, was reported by 19.5% of adults aged 18 to 34, 17.4% of those 35 to 49, 16.0% of those 50 to 64 and 12.9% of those 65 and older.

The same report found that 69.6% of adults with frequent fatigue reported anxiety symptoms and 45.0% reported depression symptoms. These are associations from a single cross-sectional survey. They show which experiences travel together, not which one comes first or causes the other.

The workup begins with conversation rather than a needle. The National Library of Medicine's consumer guide says patients are asked about their history, symptoms, habits and feelings, and that the examination focuses on the heart, lymph nodes, thyroid, abdomen and nervous system.

Medicines come next. The 2023 review states: "Medications should be reviewed to ensure the fatigue is not iatrogenic," meaning caused by treatment itself. The consumer guide names antihistamines, blood pressure medicines, sleeping pills, steroids and diuretics among drugs that may cause fatigue or drowsiness. A review identifies candidates for discussion; any change belongs to the prescriber.

Mood and sleep are screened with standard questionnaires. The review lists the nine-item Patient Health Questionnaire for depression and a seven-item anxiety tool, and says patients at high risk of obstructive sleep apnea "should be screened using a validated tool" such as the STOP-Bang questionnaire.

Blood tests follow the history rather than replacing it. The review's basic workup includes a comprehensive metabolic panel, a complete blood count and a thyroid-stimulating hormone level, with a pregnancy test, a sedimentation rate and an HIV test where appropriate; it lists hemoglobin A1c under diabetes. It adds that "laboratory testing without specific indications is not high-yield and may only change treatment in 5% of patients," which is why the history decides which tests are ordered.

Fatigue that persists past six months, with a particular pattern, meets a federal definition. The criteria published in 2015 by the Institute of Medicine, now the National Academy of Medicine, and reproduced on the Centers for Disease Control and Prevention's clinician pages, require three core features. The first is a substantial reduction in the ability to carry on pre-illness activity, lasting more than six months, with fatigue that is new in onset and not the result of ongoing exertion. The second is post-exertional malaise, a worsening of symptoms after physical, mental or emotional effort. The third is unrefreshing sleep.

At least one more feature is required: cognitive impairment or orthostatic intolerance, a worsening of symptoms on standing upright. The core symptoms must be present at least half the time with moderate or greater intensity. The 2023 review notes that no physical finding or laboratory test is specific to the condition, which is why the Oct 6 biomarker study is framed as exploratory.

The review's graded recommendations differ by patient: exercise and cognitive behavioral therapy for fatigue tied to cancer, inflammatory and neurologic conditions and fibromyalgia, but not for this syndrome, where it recommends education about pacing.

A 2023 federal data brief counted adults as affected if a clinician had told them they had the condition and they still had it. By that measure, 1.3% of adults were affected in 2021–2022, including 1.7% of women and 0.9% of men, with 2.0% among adults in their 50s and 2.1% among those in their 60s.