Causes of Constant Fatigue in Women: What to Check and When to See a Doctor

Educational information, not medical advice: see our Medical Disclaimer.

Everyone gets tired. But feeling drained for weeks, or so tired that it affects your daily life, is worth checking. MedlinePlus defines fatigue as a feeling of weariness, tiredness or lack of energy that can interfere with your usual daily activities (MedlinePlus). It’s a symptom rather than a diagnosis, and it has a long list of possible causes, from sleep and stress to iron deficiency, thyroid problems and hormonal changes. This guide covers the causes of constant fatigue in women: the most common ones, those that affect women more, what a doctor may check and when to get help.

In this article:

• What Counts as Constant Fatigue?
• The Most Common Causes
• Causes That Affect Women More
• What a Doctor May Check
• What You Can Try in the Meantime
• When to See a Doctor
• Fatigue FAQ
• Your Next Step

What Counts as Constant Fatigue?

Tiredness after a bad night or a busy week is normal. The Endocrine Society notes that tiredness can also occur as part of a normal, busy life, and that symptoms like it are common and non-specific, meaning they appear in many different conditions (Endocrine Society). The NHS lists insufficient sleep or insomnia, an unhealthy lifestyle, stress, depression, bereavement, hormonal changes, illnesses such as glandular fever and COVID-19, and certain medicines as common causes (NHS).

Fatigue becomes worth investigating when it lasts for weeks, doesn’t improve with rest, or gets in the way of daily life. Both the NHS and MedlinePlus use “weeks” as the point to get it checked (NHS; MedlinePlus).

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The Most Common Causes

These are the causes health authorities list most often. Several can occur together, which is one reason a single blood test rarely tells the whole story.

Causes That Affect Women More

Heavy periods and iron deficiency

The NHS lists heavy periods and pregnancy as common causes of iron deficiency anemia (NHS). ACOG counts bleeding that soaks through one or more pads or tampons every hour, or that lasts more than 7 days, as abnormal (ACOG). If your periods are heavy and you’re tired, mention both. Our guide to irregular periods in perimenopause explains which bleeding patterns to raise. If your bleeding is also frequent, see our guide to period every 2 weeks in perimenopause.

Thyroid problems

Hashimoto’s disease, a common cause of an underactive thyroid, is most common in women and usually starts between 30 and 50. Fatigue is one of its listed symptoms, alongside weight gain, feeling cold and low mood (NHS). Our guide to hormonal imbalance symptoms covers thyroid problems and other hormone-related conditions.

Perimenopause and menopause

ACOG says night sweats may wake you up and leave you feeling tired and sluggish during the day (ACOG). Mayo Clinic adds that trouble sleeping is often due to hot flashes or night sweats, but not always: sleep patterns can change in perimenopause even without them (Mayo Clinic). See our perimenopause symptoms checklist, our guide to how to stop hot flashes and our complete perimenopause and menopause guide. If anxiety is part of the picture, see our guide to perimenopause anxiety.

PCOS

The Office on Women’s Health links PCOS with sleep apnea, depression, anxiety and diabetes (Office on Women’s Health), all of which can cause fatigue.

Heart disease

Heart disease can look different in women. The CDC lists tiredness that won’t go away or feels excessive among women’s symptoms, and lists sudden fatigue, shortness of breath and swelling of the feet, ankles, legs or abdomen among the signs to call 9-1-1 for (CDC). Fatigue on its own has many other causes, but new, unusual tiredness alongside other symptoms shouldn’t be brushed off.

What a Doctor May Check

MedlinePlus says a provider will ask about your sleep, activities, appetite and exercise, do a physical exam, and order lab tests (MedlinePlus). Depending on your other symptoms, that can include a full blood count to check for iron deficiency anemia (NHS) and blood tests for thyroid-stimulating hormone (TSH) and thyroxine (T4) (NHS). If you snore or have been told you gasp or choke in your sleep, say so, since the NHS lists that as a reason to see a GP. A short diary of your sleep, periods and energy levels before the visit helps.

What You Can Try in the Meantime

The NHS suggests these steps for tiredness (NHS):

• Eat a healthy diet and exercise regularly.
• Keep to the same sleep times and aim for 6 to 9 hours of sleep.
• Wind down before bed, for example by reading or listening to music, and keep your bedroom comfortable.
• Avoid caffeine, food and exercise in the 2 hours before sleep, and don’t use screens in the hour before sleep.
• Don’t smoke, and don’t drink too much alcohol.
• Find ways to manage stress (MedlinePlus).

Get a blood test before assuming you’re low in iron. The NHS describes iron tablets as a treatment for diagnosed iron deficiency anemia, usually for around 6 months (NHS). Be wary, too, of an “adrenal fatigue” diagnosis or supplements sold for it. The Endocrine Society says no scientific proof exists that it is a true medical condition, and warns that supplements marketed for adrenal health lack FDA oversight and may cause harm (Endocrine Society).

When to See a Doctor

Consider booking an appointment if:

• You’ve been tired for a few weeks and aren’t sure why, or your tiredness affects your daily life (NHS).
• You’re tired and also have other symptoms, such as weight loss or mood changes (NHS).
• You’ve been told you make gasping, snorting or choking noises while you sleep (NHS).
• Your periods are heavy or last more than 7 days (ACOG).
• You feel low or hopeless much of the time. If you’re thinking about harming yourself, call or text 988 in the U.S.
• Call 9-1-1 for chest pain or discomfort, shortness of breath, dizziness, palpitations, sudden fatigue, or swelling of the feet, ankles, legs or abdomen. The CDC says not to delay (CDC).

Our appointment steps explain what to bring and what to ask.

Fatigue FAQ

Why am I always tired even after sleeping 8 hours?

Sleep length isn’t the only factor. Poor-quality sleep, sleep apnea, anemia, an underactive thyroid, depression, medicines and infections can all cause fatigue (NHS; MedlinePlus). If it lasts for weeks, get checked.

Is constant fatigue a sign of perimenopause?

It can be part of it, mainly when night sweats or sleep changes disrupt your rest (ACOG), but fatigue has many other possible causes, so it’s worth ruling them out. Our symptoms checklist can help you spot a wider pattern.

Can low iron cause tiredness?

Yes. The NHS lists tiredness and lack of energy among the common symptoms of iron deficiency anemia, alongside shortness of breath and paler skin, and heavy periods are a common cause (NHS). A full blood count checks for it.

What is adrenal fatigue?

The Endocrine Society says no scientific proof exists to support adrenal fatigue as a true medical condition. It says people given that label may actually have adrenal insufficiency, depression, obstructive sleep apnea or other health problems, so it’s worth getting the underlying cause checked (Endocrine Society).

Could it be chronic fatigue syndrome (ME/CFS)?

The CDC describes ME/CFS as a serious, often long-lasting illness with severe fatigue not improved by rest, symptoms that can get worse after physical or mental activity, sleep problems and trouble thinking. Women are affected more often than men, there is no specific test, and more than 9 in 10 people with ME/CFS have not been diagnosed (CDC). If that pattern sounds familiar, tell your doctor.

Your Next Step

For a couple of weeks, note when you’re tired, how you’re sleeping, your period pattern and any other symptoms, then book a visit and bring your notes. For related reading, see our guides on hormonal imbalance symptoms, irregular periods in perimenopause, the perimenopause symptoms checklist, how to stop hot flashes and our complete perimenopause and menopause guide.

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Sources: Tiredness and fatigue — NHS · Fatigue — MedlinePlus · Iron deficiency anaemia — NHS · Underactive thyroid — NHS · Women and heart disease — CDC · ME/CFS — CDC · The Menopause Years — ACOG · Abnormal uterine bleeding — ACOG · Perimenopause — Mayo Clinic · Polycystic ovary syndrome — Office on Women’s Health · Adrenal fatigue — Endocrine Society · Featured image: Shixart1985 / Wikimedia Commons (CC BY 2.0)

About the author: Jessica Bordo writes Daily Health Cycle, where she shares practical, evidence-based women’s health information. Articles are informed by sources such as the NHS, CDC and Mayo Clinic, and we link to our main sources. No medical reviewer is listed for this article, so use it to prepare questions for your own clinician, not to replace their advice. Our authors page explains how we approach accuracy and disclaimers.

This article is for general education and isn’t medical advice. Read our Medical Disclaimer and talk with a qualified clinician about your own care.

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