The Hidden Causes of Anemia in Women You Shouldn't Miss

Anemia in women is frequently brushed off as “just iron deficiency,” especially during menstruating years. But in reality, anemia is often the final symptom of a much more complex clinical problem. When a woman presents with fatigue, palpitations, pallor, or shortness of breath—and her hemoglobin is low—the knee-jerk assumption is usually nutritional. But what if it's not? What if the iron pills don’t work? What if there’s something more insidious—or simply overlooked?
This piece dives into the often-hidden, frequently-missed causes of anemia in women, especially when standard therapies fail. This isn’t about memorizing MCV patterns or reflex ordering of iron studies—it’s about the clinical reasoning that uncovers what’s really going on. After reading this, “just another anemic female patient” will never feel routine again.

Why Anemia Is Often Underestimated in Women

From adolescence through menopause and beyond, women experience a cascade of physiological demands and pathological risks that predispose them to anemia. Menstruation, pregnancy, lactation, rapid hormonal shifts, common dieting practices, and even cultural food patterns make women unique in their vulnerability.

Yet, despite this, anemia in women is underdiagnosed and under-investigated. Many patients are dismissed as “non-compliant” if they don’t improve on iron supplements, while others are subjected to unnecessary referrals and irrelevant tests. For physicians and medical students alike, the challenge lies in knowing what else to consider when the obvious answers don’t fit.

Silent Gastrointestinal Blood Loss (Not Just in Men)

GI bleeding is often viewed as a male-dominant issue, associated with NSAID use, alcohol, or malignancy. However, women can experience chronic occult blood loss too—often overlooked due to age or gender biases. Common culprits include:

• Celiac disease causing chronic malabsorption and occult blood loss
  
  
• Helicobacter pylori infections leading to gastritis and mucosal injury
  
  
• NSAID use for menstrual pain resulting in gastric erosions or ulcers
  
  
• Early-stage IBD or colon polyps
  
  
• Vascular lesions such as angiodysplasia, especially in older women
  

Any woman—especially postmenopausal or amenorrheic—with persistent iron deficiency should be screened for GI blood loss. Normal endoscopic appearances don't rule out subtle bleeding sources. Occult blood testing or capsule endoscopy may be warranted.

Heavy Menstrual Bleeding (That No One Quantifies)

“Do you have heavy periods?”
“No, I think they’re normal.”

This dialogue is nearly universal. Most women do not recognize heavy menstrual bleeding because it has always been their norm. That’s where clinical curiosity matters.

Key questions to ask include:

• How many pads or tampons per day?
  
  
• Do you soak through clothes or bedding?
  
  
• Do you need to double up pads?
  
  
• Do you pass clots or feel lightheaded during menstruation?
  

Potential underlying causes include:

• Uterine fibroids
  
  
• Endometriosis or adenomyosis
  
  
• PCOS with breakthrough heavy bleeding
  
  
• Coagulopathies like Von Willebrand disease
  

The Pictorial Blood Loss Assessment Chart (PBAC) can be a useful tool in practice. Don’t forget that even younger women may have inherited bleeding disorders that have simply never been considered.

Malabsorption Syndromes That Mask Themselves Well

Some women eat appropriately but don’t absorb key nutrients. In these cases, anemia is often the tip of the iceberg. Malabsorption-related causes include:

• Celiac disease (often silent or presenting with vague GI discomfort)
  
  
• Crohn’s disease affecting nutrient-absorbing areas of the gut
  
  
• Bariatric surgery leading to iron, B12, and folate malabsorption
  
  
• Chronic pancreatitis resulting in enzyme insufficiency
  
  
• Short bowel syndrome from prior surgeries or congenital issues
  

Red flags include:

• Persistent anemia despite adequate oral supplementation
  
  
• Coexisting B12 or folate deficiency
  
  
• Mild GI symptoms, brittle nails, weight loss, glossitis
  

Pay attention to the subtle signs. Many of these patients “look fine” but live in a constant state of subclinical depletion.

Inflammatory and Chronic Diseases That Steal Iron

Anemia of chronic disease (ACD) is frequently missed in women, especially when iron studies appear “normal.” Common conditions include:

• Rheumatoid arthritis and other autoimmune diseases
  
  
• Endometriosis, where chronic inflammation impacts iron metabolism
  
  
• lupus, where anemia may also be compounded by renal dysfunction
  
  
• Chronic infections like tuberculosis
  
  
• Diabetes with nephropathy or CKD
  

The trap? Ferritin may appear normal or even high due to its role as an acute phase reactant. This masks functional iron deficiency. Always interpret ferritin alongside CRP or ESR. Chronic inflammation increases hepcidin, which traps iron in storage and reduces its availability for erythropoiesis.

Undiagnosed Hypothyroidism and its Anemic Shadows

Many hypothyroid patients are not overtly anemic—until you look closer. Women presenting with fatigue, weight gain, or cold intolerance often have a TSH checked. But anemia can be one of the earliest or most prominent features of hypothyroidism.

Mechanisms include:

• Normocytic or hypochromic anemia
  
  
• Impaired iron utilization
  
  
• Pernicious anemia due to autoimmune gastritis (linked with Hashimoto’s)
  

Consider additional clues:

• Macrocytic or mixed anemia
  
  
• Positive thyroid autoantibodies
  
  
• Neurological symptoms like paresthesias or ataxia
  

Correcting the thyroid dysfunction often improves the anemia—something iron alone could never achieve.

Chronic Blood Donation or Phlebotomy-Induced Anemia

Women who donate blood frequently—especially in communities where replacement iron is not routinely advised—may develop gradual iron depletion. This is often missed, especially in those who appear healthy otherwise.

Therapeutic phlebotomy, used in conditions like hemochromatosis or polycythemia vera, can also cause secondary anemia in women if not monitored with care. Always ask:

• Do you donate blood regularly?
  
  
• Are you receiving treatment that involves blood removal?
  

Low transferrin saturation, low ferritin, and elevated RDW are often seen in these cases.

Dietary Patterns and Cultural Restrictions

It’s not just what patients eat—it’s what they avoid.

Red meat is often restricted due to religious, ethical, or personal reasons. Add to that:

• Vegan or vegetarian diets with inadequate B12
  
  
• Tea or coffee during meals (which impair iron absorption)
  
  
• Caloric restriction for weight loss
  
  
• Disordered eating patterns
  

These patients may present with:

• Microcytic anemia with low serum iron and ferritin
  
  
• Concurrent zinc or vitamin C deficiency
  
  
• B12 deficiency manifesting as glossitis or neuropathy
  

A thorough dietary history is key. Lab work may show you the end-result, but the story lies in the kitchen.

Pregnancy-Related Anemia That Never Resolves

Pregnancy triples iron requirements. Many women don’t fully recover their iron stores postpartum—especially when pregnancies are closely spaced or when they breastfeed for extended periods.

Contributing factors:

• Missed postpartum follow-up
  
  
• Iron intolerance (especially GI upset with ferrous sulfate)
  
  
• Cultural taboos around iron supplements
  
  
• Nutritional gaps due to fatigue or caregiving demands
  

Symptoms like fatigue, hair thinning, and poor concentration can persist for months postpartum. Always check ferritin, not just hemoglobin, in women post-delivery—even if they appear outwardly well.

Hemolysis That Hides in Plain Sight

Not all anemia is about loss or poor intake. Some is about destruction.

Hemolytic anemia can be chronic, subtle, and easily missed. In women, causes include:

• G6PD deficiency triggered by infection or drugs
  
  
• Autoimmune hemolytic anemia (idiopathic or secondary to SLE)
  
  
• Hereditary spherocytosis diagnosed late in life
  
  
• Pregnancy-related hemolysis like HELLP
  
  
• Drug-induced hemolysis (e.g., antibiotics, anti-malarials)
  

Key investigations include:

• Elevated LDH
  
  
• High indirect bilirubin
  
  
• Increased reticulocyte count
  
  
• Decreased haptoglobin
  

Don’t wait for a full-blown crisis. Hemolysis can be slow, and patients may adapt without clear signs—until you look at the labs.

Bone Marrow Suppression or Infiltration

Though rare, these diagnoses are critical not to miss.

Bone marrow pathology may present subtly as:

• Aplastic anemia
  
  
• Myelodysplastic syndromes
  
  
• Leukemia or lymphoma
  
  
• Marrow infiltration from metastatic cancer
  

Red flags:

• Pancytopenia
  
  
• Fatigue with infections and bruising
  
  
• Splenomegaly or lymphadenopathy
  
  
• Abnormal peripheral smear
  

A bone marrow biopsy is warranted when anemia is unexplained and persistent despite workup.

Final Clinical Pearl: Always Think Beyond Hemoglobin

Hemoglobin is a snapshot, not a narrative. Many women have “normal” hemoglobin but exhausted iron stores. Others walk into your clinic looking fine, yet are carrying the physiological burden of multiple compounding deficiencies.

Never dismiss vague complaints of fatigue in menstruating women. High RDW, low-normal ferritin, and persistent symptoms demand a deeper look. The consequences of missing the real cause? Poor quality of life, delayed diagnoses, infertility, cognitive decline, and missed underlying disease.