Why Am I So Tired? What Every Woman Needs to Know Before Blaming Burnout

May is here, and all month long we’re talking about one of the most common — and most dismissed — complaints I hear from women of every age: fatigue. Not the kind that goes away after a good night’s sleep. The kind that sits in your chest before your feet even hit the floor. The kind that makes you wonder if this is just… your life now?

It doesn’t have to be. And it starts with asking the right questions.

---

Let’s Get One Thing Straight First

Fatigue is not a personality flaw. It is not proof that you can’t handle your life. And it is absolutely not something you should have to just push through.

It is a symptom, and like every symptom, it deserves a real evaluation.

Here’s the problem: fatigue is one of the most common reasons women visit a doctor, and one of the most commonly under-evaluated. It’s easy for both patients and providers to chalk it up to “stress” or “getting older” or “just life.” And sometimes those things are contributing. But sometimes, more often than we think, there’s a real, identifiable, treatable cause sitting right there in your bloodwork, waiting to be found.

This week, we’re starting at the foundation: before we talk about sleep hygiene, nutrition, and stress (all of which we’ll cover this month), we need to talk about ruling out the medical causes of fatigue that are commonly missed. Because no amount of self-care fixes an undiagnosed thyroid problem or an iron deficiency. And no amount of sleep helps when sleep apnea is quietly fragmenting every hour of rest you think you’re getting.

So let’s walk through the workup that I order for my own patients

---

First: What Kind of Tired Are You?

Before we get into labs and diagnoses, it helps to get more specific about what “fatigue” actually means for you. These are the questions I’d be asking you in the office, because the character of the fatigue gives us clues:

Are you sleepy — or are you exhausted?
There’s a difference. Sleepiness is the urge to fall asleep. Exhaustion is a deeper physical depletion that rest doesn’t always fix.

Is it physical, or is it mental?
Muscle weakness, heaviness, breathlessness with activity — those are physical signals. Brain fog, difficulty concentrating, low motivation, emotional flatness — those can point toward depression, thyroid dysfunction, or nutritional deficiencies.

When did it start, and how long has it been?
Fatigue that’s been building gradually over months is different from fatigue that began suddenly. Fatigue lasting more than six months requires a more thorough investigation.

What makes it better or worse?
Does rest help at all? Does it worsen with activity? Does it fluctuate? These details matter.

Write your answers down before your next appointment. Your doctor will be grateful, and you’ll get more out of the visit.

---

The Medical Causes We Don’t Want to Miss

The American Academy of Family Physicians recognizes fatigue as one of the top ten reasons patients visit primary care offices — and yet studies show that in many cases, a clear diagnosis explaining the fatigue is never established, not because it doesn’t exist, but because the workup wasn’t thorough enough. I am not knocking your doctor here. Within the traditional healthcare setting, it is nearly impossible to dedicate the needed time to tease out something as complex as fatigue. Especially in a single appointment.

Here are the causes that deserve a seat at the table.

---

1. Iron Deficiency — With or Without Anemia

Most people know that anemia — low hemoglobin — can cause fatigue. But what many women don’t know, and what many clinicians overlook, is that iron deficiency itself causes fatigue even before anemia develops. Iron does far more than carry oxygen in your red blood cells. It’s essential for energy metabolism at the cellular level, for neurotransmitter production, for thyroid function, and for mitochondrial health. When your iron stores are depleted, your body feels it — even when your hemoglobin is still in the normal range.

The test you want: serum ferritin. This is the marker that reflects your iron stores. A standard CBC (complete blood count) alone is not enough. Hemoglobin can remain normal while ferritin is low, and that gap is where so many women fall through the cracks.

The ferritin threshold is also evolving in the literature. A ferritin below 30 µg/L has traditionally been the marker for iron deficiency, but emerging evidence suggests that values below 50 µg/L can still be associated with physiologically significant depletion — particularly in premenopausal women, who lose iron with every menstrual cycle.

Who is most at risk?

• Women with heavy menstrual periods
• Women with any history of bleeding disorders
• Women who are pregnant or recently postpartum
• Vegetarians and vegans (non-heme iron is less bioavailable)
• Frequent blood donors
• Women with gut conditions affecting absorption (Crohn’s, celiac, gastric bypass)

Ask your doctor for: CBC and serum ferritin. If ferritin is low-normal and you have symptoms, that conversation is worth having.

---

2. Thyroid Dysfunction

The thyroid regulates how every cell in your body produces and uses energy. When it’s underperforming — hypothyroidism — everything slows down. Fatigue, brain fog, weight gain, feeling cold when others don’t, dry skin, and hair changes can all be part of the picture. The most common cause in the US is Hashimoto’s thyroiditis, an autoimmune condition that disproportionately affects women and can develop gradually over years.

According to ATA/AACE guidelines, TSH is the single best first-line screening test for thyroid dysfunction in an outpatient setting. If TSH is elevated, Free T4 is the appropriate next step to clarify the picture. One thing worth knowing: you may see content online promoting “full thyroid panels” including Free T3 as essential for everyone — current guidelines do not support routine Free T3 testing to diagnose hypothyroidism. Testing free T3 is nuanced and may be appropriate for some but it patient dependent so talk to your own doctor first. If autoimmune thyroid disease is specifically suspected based on your history or exam, TPO antibody testing is a reasonable addition to that conversation.

If your TSH comes back mildly elevated but your Free T4 is normal, that’s called subclinical hypothyroidism — and whether to treat it is, again, a nuanced, individualized decision made with your physician. It’s not automatically treated, and it’s not something to resolve based on a symptom quiz.

Ask your doctor for: TSH. If it’s elevated, the conversation continues from there with your provider guiding next steps.

---

3. Obstructive Sleep Apnea

Sleep apnea in women is vastly underdiagnosed — partly because the classic presentation we learned in medical training (overweight, middle-aged man who snores loudly) does not describe most women with the condition.

Women with obstructive sleep apnea (OSA) often present differently: they may report fatigue, insomnia, morning headaches, mood changes, and brain fog more than they report snoring or witnessed apneas. This means they’re frequently evaluated for depression, hypothyroidism, or anxiety first — and the OSA goes undiagnosed for years.

What’s happening physiologically: during sleep, the airway repeatedly collapses, causing brief arousals from sleep that the person often doesn’t remember. The result is fragmented, non-restorative sleep — even if you were in bed for eight hours. Oxygen levels drop with each episode, and over time this has real cardiovascular and metabolic consequences.

Risk factors in women include: obesity, menopause (declining estrogen and progesterone reduce airway tone), polycystic ovary syndrome (PCOS), and hypothyroidism. Postmenopause, the prevalence of OSA in women approaches that of men.

If you’re waking up exhausted despite what feels like adequate sleep, waking with headaches, needing naps to function, or your partner has noticed anything unusual during your sleep — this is worth discussing. A home sleep test or in-lab polysomnography can establish the diagnosis. And if OSA is confirmed, treating it can be genuinely life-changing.

Ask your doctor about: OSA screening, especially if you’re perimenopausal or postmenopausal, have gained weight, or don’t feel refreshed after sleep.

---

4. Depression and Anxiety

I include these here not to dismiss them as “not real” but actually quite the opposite. Depression is a physiological condition with profound effects on energy, sleep, concentration, and motivation, and it deserves the same rigorous attention as any other diagnosis on this list.

Fatigue is one of the hallmark symptoms of depression and it’s frequently the presenting complaint that brings someone to the doctor. What makes this tricky is the bidirectionality: fatigue causes depression, and depression causes fatigue. Unresolved iron deficiency, thyroid dysfunction, and sleep apnea all increase the risk of depressive symptoms. Treating the underlying condition sometimes resolves the mood symptoms but sometimes it doesn’t, and direct treatment of depression is needed.

A validated screening tool like the PHQ-9 is a simple, evidence-based starting point. If your provider hasn’t asked you these questions during a fatigue evaluation, you can ask them to.

A note on anxiety: chronic anxiety is also energy-expensive. The body running on a low-level threat response is burning fuel constantly, leaving less available for daily functioning. This is real and worth naming.

---

5. Blood Sugar Dysregulation and Diabetes

Persistently high blood glucose or blood sugar that swings significantly is a significant driver of fatigue. Cells can’t use glucose efficiently without adequate insulin, and the resulting energy deficit is felt throughout the body.

Undiagnosed Type 2 diabetes and prediabetes are extremely common and frequently asymptomatic in the early stages. Fatigue, frequent urination, increased thirst, and blurry vision can all be early signals.

Fasting glucose and/or HbA1c (a 3-month average of blood sugar) are standard parts of preventive screening and should be included in a fatigue workup if not recently checked.

---

6. Nutritional Deficiencies Beyond Iron

Vitamin B12: Essential for nerve function and red blood cell production. Deficiency causes fatigue, brain fog, and tingling in the extremities. At particular risk: vegans and vegetarians (B12 is found almost exclusively in animal products), women on long-term metformin (which impairs B12 absorption), and those with gut absorption issues.

Vitamin D: Evidence on vitamin D and fatigue is mixed — deficiency is unlikely to be the sole cause of fatigue, but it’s prevalent, worth checking if not recently done, and part of a complete picture.

Magnesium: Involved in hundreds of enzymatic processes including energy metabolism. Many women don’t get enough through diet. Not always tested on standard panels, but worth discussing with your provider.

---

7. Other Conditions Worth Considering

Depending on your history and symptoms, the workup may extend to include:

• Autoimmune conditions (lupus, rheumatoid arthritis, Sjögren’s syndrome) — these disproportionately affect women and fatigue is a cardinal feature
• Celiac disease — particularly if GI symptoms, anemia, or skin issues are present
• Chronic infections (hepatitis B and C, HIV) — all can cause persistent fatigue and should be screened based on risk and guidelines
• Adrenal insufficiency — rare but serious; consider if fatigue is accompanied by salt craving, low blood pressure, and unexplained weight loss
• Cancer — unexplained fatigue, especially with unintentional weight loss, night sweats, or lymphadenopathy, warrants age-appropriate cancer screening and prompt follow-up

---

Your Fatigue Workup Checklist

Here is a reasonable starting framework for what a thorough initial evaluation of unexplained fatigue might include. This is meant to be a conversation guide with your provider, not a self-ordering checklist as your individual history and exam should always guide what’s appropriate for you.

History:

• Duration, onset, and severity of fatigue
• Quality of sleep (hours, feeling rested, snoring, waking)
• Menstrual history (cycle regularity, heaviness, recent changes)
• Mood (PHQ-9 screening)
• Medications and supplements (including beta blockers, antihistamines, and benzodiazepines — all can cause fatigue)
• Diet and recent changes in weight
• Family history of thyroid disease, autoimmune conditions, diabetes

Physical Exam:

• Vital signs including heart rate and blood pressure
• Thyroid palpation
• Conjunctival pallor (a sign of anemia)
• Lymph node assessment
• Cardiopulmonary exam

Initial Labs:

• CBC (complete blood count)
• Serum ferritin
• TSH (and Free T4, thyroid antibodies if indicated)
• Comprehensive metabolic panel (kidney function, liver function, calcium, glucose)
• HbA1c or fasting glucose
• Vitamin B12
• Vitamin D (25-OH)

Consider Based on Clinical Picture:

• Iron panel (serum iron, TIBC, transferrin saturation)
• ESR/CRP (inflammatory markers)
• ANA (if autoimmune disease suspected)
• Celiac antibodies (if GI symptoms or unexplained anemia)
• Sleep study (home or in-lab) if OSA is suspected
• Age-appropriate cancer screening if not current

---

What If Everything Comes Back Normal?

This happens and it can be incredibly frustrating. You know something is wrong, and the numbers say otherwise. A few things to keep in mind:

First, “normal” is a range, and where you fall within that range matters. A ferritin of 14 is technically “normal” in many lab reference ranges, but for a menstruating woman with fatigue, it deserves attention. Bring your actual values to the conversation, not just the “normal” flag.

Second, if standard labs are unremarkable, it doesn’t mean fatigue isn’t real but it does mean the cause may lie in the lifestyle and psychosocial territory we’re going to spend the rest of this month exploring. Sleep quality, nutritional patterns, chronic stress, sedentary habits, screen time (!!) and social isolation are all evidence-based drivers of fatigue, and they don’t show up in bloodwork.

Third, follow up. A single appointment is not enough. Fatigue can be a moving target, and a provider who schedules a return visit rather than sending you home with a “you’re fine” — is doing right by you.

---

The Takeaway

Fatigue is not something you should normalize, dismiss, or power through without asking why. You deserve a real evaluation, one that looks beyond the obvious and digs into the full picture.

A thorough history. A physical exam. The right lab work. And a doctor who listens.

That’s the starting point. And that’s what you deserve.

---

Next week, we’re going deep on sleep — not just how much you’re getting, but the quality, the architecture, and what’s quietly stealing your rest. Because for many women, the answer to fatigue isn’t more hours in bed. It’s understanding what’s happening during the hours you’re already there.

---

As always, this content is for educational purposes and is not a substitute for individualized medical care. If you are experiencing persistent fatigue, please discuss it with your healthcare provider.