Why Am I Always Tired? Common Causes of Fatigue in Women

What conditions most commonly cause fatigue in women?

Biology, hormones, and caregiving load all intersect to make fatigue particularly common — and particularly complex — in women.

Iron-deficiency anemia is one of the most common correctable causes. Monthly blood loss through menstruation, pregnancy, and breastfeeding all raise iron requirements. Iron carries oxygen to cells; when it drops too low, the whole body runs slow 1Ref 1Leung AKC, Lam JM, Wong AHC, Hon KL, Li X (2024).Iron Deficiency Anemia: An Updated Review.Iron-deficiency anemia as a leading cause of fatigue in women who menstruate; ferritin as the relevant marker. Ferritin (stored iron) can be low even before a standard blood count looks abnormal — so ferritin testing matters.

Thyroid disease — particularly hypothyroidism — is several times more common in women than men. An underactive thyroid slows nearly every body process, causing fatigue, weight gain, feeling cold, and brain fog 2Ref 2Jonklaas J, Bianco AC, Bauer AJ, et al. (2014).Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement.Hypothyroidism as a common, treatable cause of fatigue in women; TSH as the appropriate screening test; thyroid hormone replacement as effective treatment. A single blood test (TSH) screens for it.

Hormonal shifts throughout the menstrual cycle, and more dramatically through perimenopause and menopause, can directly disrupt sleep and energy 3Ref 3Faubion SS, Crandall CJ, Davis L, El Khoudary SR, Hodis HN, Lobo RA, Maki PM, Manson JE, Pinkerton JV, Santoro NF, Shifren JL, Shufelt CL, Thurston RC, Wolfman W (2022).The 2022 Hormone Therapy Position Statement of The North American Menopause Society.Hormonal changes during perimenopause and menopause disrupt sleep and contribute to fatigue in women. Night sweats fragment sleep and leave women exhausted the next day.

Depression disproportionately affects women and causes real, physical exhaustion — not just emotional heaviness. The USPSTF recommends routine screening for depression in all adults precisely because it is common and often presents as fatigue rather than low mood 4Ref 4O'Connor E, Henninger M, Perdue LA, et al. (2023).Screening for Depression and Suicide Risk in Adults: US Preventive Services Task Force Recommendation Statement.USPSTF recommendation for routine depression screening in adults; depression as a common and treatable cause of fatigue.

Vitamin and mineral deficiencies — particularly vitamin B12 5Ref 5Obeid R, Andrès E, Češka R, et al. (2024).Diagnosis, Treatment and Long-Term Management of Vitamin B12 Deficiency in Adults: A Delphi Expert Consensus.B12 deficiency as a common, correctable cause of fatigue, particularly in those on plant-based diets, vitamin D 6Ref 6Di Molfetta IV, Bordoni L, Gabbianelli R, Sagratini G, Alessandroni L (2024).Vitamin D and Its Role on the Fatigue Mitigation: A Narrative Review.Vitamin D deficiency as a frequent and correctable cause of fatigue in women, and magnesium — are common and often detectable with blood tests.

Sleep disorders including insomnia and obstructive sleep apnea are underdiagnosed in women. Sleep apnea in particular presents differently in women than in men — less often as loud snoring and more often as fatigue, insomnia, or mood changes — so it is frequently missed 7Ref 7Kapur VK, Auckley DH, Chowdhuri S, et al. (2017).Clinical Practice Guideline for Diagnostic Testing for Adult Obstructive Sleep Apnea: An American Academy of Sleep Medicine Clinical Practice Guideline.Obstructive sleep apnea as an underdiagnosed cause of fatigue, with different presentation in women than in men.

ME/CFS (myalgic encephalomyelitis/chronic fatigue syndrome) affects women disproportionately. Its hallmark is profound fatigue that worsens after physical or mental effort (post-exertional malaise), unrefreshing sleep, and cognitive difficulties lasting more than six months 8Ref 8Committee on the Diagnostic Criteria for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome, Board on the Health of Select Populations, Institute of Medicine (2015).Beyond Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Redefining an Illness.ME/CFS diagnostic criteria including post-exertional malaise and unrefreshing sleep as hallmarks; disproportionate impact on women.

Why do lifestyle factors compound the picture for women?

Even when a medical cause is present, daily patterns often make things worse. Carrying disproportionate caregiving and household responsibilities, chronic sleep debt, irregular eating, and sustained stress create a fatigue burden that is greater than any single cause.

A few specific patterns worth noting:

• Undereating or restrictive eating reduces the fuel available for energy. Skipping meals — even when managing weight — can cause significant tiredness.
• Disrupted sleep from young children, shift work, anxiety, or pain compounds every other cause.
• High caffeine intake can create a stimulant-withdrawal loop that leaves people feeling worse overall.

These are not lifestyle choices to be corrected through willpower. They are real biological drivers of fatigue, and they are worth naming to a clinician.

What does a clinical evaluation for fatigue in women typically involve?

If fatigue has lasted more than two to three weeks, is not explained by obvious causes, or is getting in the way of daily life — a clinician visit is worthwhile.

A clinician will typically start with a focused history, then order some or all of: a complete blood count (for anemia), TSH (thyroid), iron and ferritin, vitamin B12 and D, and a basic metabolic panel. A validated depression screen such as the PHQ-9 is often part of the evaluation 9Ref 9Kroenke K, Spitzer RL, Williams JBW (2001).The PHQ-9: Validity of a Brief Depression Severity Measure.PHQ-9 as a validated instrument used in clinical evaluation of fatigue when depression is suspected. Depending on what this panel shows, hormonal testing, a sleep study, or further workup may follow.

Many causes of fatigue in women are very treatable — iron supplementation for deficiency, thyroid hormone replacement for hypothyroidism 2Ref 2Jonklaas J, Bianco AC, Bauer AJ, et al. (2014).Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement.Hypothyroidism as a common, treatable cause of fatigue in women; TSH as the appropriate screening test; thyroid hormone replacement as effective treatment, therapy and medication for depression 4Ref 4O'Connor E, Henninger M, Perdue LA, et al. (2023).Screening for Depression and Suicide Risk in Adults: US Preventive Services Task Force Recommendation Statement.USPSTF recommendation for routine depression screening in adults; depression as a common and treatable cause of fatigue. The key is identifying which driver — or which combination — is actually present.

Are there situations where fatigue in women needs prompt attention?

Most fatigue is not an emergency, but certain patterns call for prompt care. These include shortness of breath at rest or with light activity, chest pain or palpitations, fatigue with rapidly progressing weakness, or unexplained weight loss. If fatigue comes alongside thoughts of self-harm or not wanting to be here, please reach out to the 988 Suicide and Crisis Lifeline by calling or texting 988.