Iron-Deficiency Anemia in Ambulatory Care

Learning objectives#

• Confirm that anemia and iron depletion are both present before assigning an iron-deficiency diagnosis.
• Build a cause-based differential that considers blood loss, malabsorption, intake, inflammation, and inherited microcytosis.
• Use celiac serology and gastrointestinal evaluation in a sequence that preserves diagnostic accuracy.
• Connect iron replacement to a monitoring plan and a search for the cause rather than treating the laboratory value alone.
• Integrate menstrual history, patient preferences, nutrition access, and alarm features without allowing one detail to close the case.

Initial presentation#

A 46-year-old woman schedules an office visit for three months of fatigue, reduced exercise tolerance, headaches, and a new habit of chewing ice, and she has not fainted and has no chest pressure or shortness of breath at rest. She reports two loose stools most mornings and intermittent bloating for about a year. There is no visible blood in the stool, black stool, vomiting, persistent abdominal pain, or unintentional weight loss.

She menstruates every 27 to 30 days. Bleeding lasts five days, is heaviest on the first day, and has not recently changed. She does not soak through products hourly, pass large clots, or bleed between periods. She eats little red meat but does eat beans, greens, eggs, and fish. She uses an over-the-counter anti-inflammatory medicine several times per month for headaches. Her sister has autoimmune thyroid disease. No relative is known to have celiac disease, colorectal cancer, or an inherited anemia.

Vital signs are stable. Conjunctivae are pale. There is no jaundice, lymph-node enlargement, or glossitis. There is no cardiac murmur, abdominal mass, focal tenderness, or edema. A complete blood count ordered before the visit shows hemoglobin 10.1 g/dL, mean corpuscular volume 74 fL, elevated red-cell distribution width, a normal white-cell count, and mild thrombocytosis. The laboratory's earlier record shows hemoglobin 12.8 g/dL two years ago.

Problem representation#

This is a hemodynamically stable adult with acquired microcytic anemia, symptoms compatible with reduced oxygen-carrying capacity, pica, and chronic gastrointestinal symptoms. Menstrual blood loss and limited heme-iron intake may contribute, but neither is clearly sufficient. The combination of microcytosis, pica, and a fall from the prior hemoglobin makes iron deficiency likely; the immediate questions are whether iron depletion is confirmed, whether there is urgent instability or active bleeding, and which source of loss or impaired absorption requires evaluation.

Prioritized differential#

1. Iron-deficiency anemia from chronic blood loss#

Reasoning for: Acquired microcytosis, elevated red-cell distribution width, pica, and mild reactive thrombocytosis fit iron deficiency. Menstruation is one possible source. Occult gastrointestinal bleeding must remain in view even without visible blood. The source can be peptic disease, medication-related injury, or a polyp. It can be cancer, inflammatory bowel disease, or another lesion.

Reasoning against or still uncertain: The menstrual history is not clearly heavy, and no overt gastrointestinal bleeding is reported. Absence of visible blood does not exclude slow gastrointestinal loss. Iron studies are needed before assigning the mechanism.

2. Celiac disease with impaired iron absorption#

Reasoning for: Chronic loose stools, bloating, and iron deficiency create a plausible malabsorption pattern. Adults with celiac disease may have subtle gastrointestinal symptoms or present through iron deficiency. A family tendency toward autoimmune disease modestly supports consideration but is not diagnostic.

Reasoning against or still uncertain: The symptoms are nonspecific, weight is stable, and there is no known family case. Celiac disease cannot be diagnosed by symptoms alone. Serology must be interpreted with total immunoglobulin A status and ongoing gluten intake, with small-bowel biopsy generally used for adult confirmation when serology is positive.

3. Upper gastrointestinal loss related to peptic disease or Helicobacter pylori#

Intermittent anti-inflammatory medicine use raises concern for mucosal injury, although use is not daily and there is no epigastric pain. Helicobacter pylori can contribute to iron deficiency. The sequence of noninvasive testing and endoscopy depends on symptoms and the broader evaluation.

4. Colorectal neoplasia, polyp, or inflammatory bowel disease#

These diagnoses have lower probability than iron deficiency itself but higher consequence if missed. Age, new anemia, and bowel symptoms shape the workup. So do family history, inflammatory markers, and the shared decision about endoscopy. Lack of weight loss or visible bleeding lowers concern somewhat but does not remove it.

5. Gynecologic blood loss#

Regular menstruation may account for some iron loss. Focused history must still assess product use, flooding, clots, bleeding duration, intermenstrual or postcoital bleeding, pregnancy possibility, fibroid symptoms, and bleeding disorders, though the current history does not establish heavy menstrual bleeding, so it should not become a convenient final answer.

6. Anemia of inflammation, thalassemia trait, or another hematologic process#

Inflammation can lower serum iron and distort ferritin upward, often with a normal or high ferritin rather than clear depletion. Thalassemia trait can cause marked microcytosis, but the acquired fall in hemoglobin, high red-cell distribution width, and pica favor iron deficiency. Both can coexist. Kidney disease, hemolysis, marrow disease, and deficiencies of other nutrients become more relevant if the initial pattern is discordant or response is poor.

Focused history and examination#

Every question you ask should identify a cause, a complication, or a treatment constraint.

• Severity and urgency: Ask about fainting, chest pressure, breathlessness at rest, palpitations, rapid worsening, active bleeding, black stool, vomiting blood, and pregnancy. These findings can shift an office evaluation to urgent care.
• Blood loss: Quantify menstrual bleeding without euphemism. Ask about gastrointestinal and urinary blood, frequent nosebleeds, easy bruising, blood donation, surgery, pregnancy, and postpartum loss.
• Gastrointestinal pattern: Clarify stool frequency, nocturnal symptoms, urgency, pain, reflux, early satiety, swallowing difficulty, weight change, mouth ulcers, skin rash, and family history of celiac disease, inflammatory bowel disease, or gastrointestinal cancer.
• Diet and absorption: Review iron-containing foods, food insecurity, dietary restrictions, bariatric or intestinal surgery, chronic acid-suppression therapy, and prior iron response. Do not infer deficiency from diet alone.
• Medicines: Record all anti-inflammatory medicines, antiplatelet drugs, anticoagulants, acid suppressants, and supplements. Ask how often each is actually taken.
• Background probability: Review prior blood counts, pregnancy history, ethnicity and family history relevant to inherited microcytosis, chronic inflammatory conditions, kidney disease, and malignancy history.

The examination repeats vital signs and assesses orthostatic symptoms when appropriate, pallor, jaundice, mouth and tongue, heart rate and flow murmur, lymph nodes, abdomen, skin, and signs of chronic disease. Rectal, pelvic, or other intimate examination is performed only when indicated. It must also be explained, consented to, and likely to change the plan.

Diagnostic strategy#

Confirm the pattern#

The first group of tests answers two questions for you, whether this is iron deficiency and whether another process is visible:

• repeat complete blood count with red-cell indices;
• reticulocyte count and peripheral smear;
• ferritin, serum iron, transferrin or total iron-binding capacity, and transferrin saturation;
• kidney and liver tests, with an inflammatory marker when inflammation could affect ferritin;
• targeted testing for pregnancy, vitamin B12, folate, hemolysis, or inherited microcytosis when the history or initial results support it.

Ferritin is the most useful single marker of iron stores, but it is also an acute-phase reactant. A clearly low value supports depletion. A value that looks normal during inflammation may not exclude iron deficiency, so the whole iron profile and context matter. The AGA guideline recommends a ferritin cutoff of 45 ng/mL rather than 15 ng/mL when diagnosing iron deficiency in patients with anemia, while recognizing that clinical context still matters.

Find the cause without erasing the signal#

Because celiac disease is plausible, the clinician orders tissue transglutaminase immunoglobulin A and total immunoglobulin A while the patient continues her usual gluten-containing diet. If immunoglobulin A is deficient, an appropriate immunoglobulin G based strategy is needed. Starting a gluten-free diet before testing can lower antibody levels and reduce biopsy yield.

Gastrointestinal evaluation is discussed rather than postponed until after months of iron treatment. AGA strongly recommends bidirectional endoscopy for men and postmenopausal women with iron-deficiency anemia and conditionally suggests it for premenopausal women, with shared decision-making. This patient also has chronic gastrointestinal symptoms and no convincing single source, so evaluation is tailored to those facts rather than menstruation status alone.

A stool blood test is not used as a substitute for diagnostic endoscopy when the clinical decision is to investigate established iron-deficiency anemia. Capsule endoscopy is not an automatic first study in an uncomplicated patient before standard evaluation and a treatment trial. Tests for Helicobacter pylori and further small-bowel evaluation are sequenced according to findings and current guidance.

Progressive results and interpretation#

Repeat testing confirms hemoglobin 9.9 g/dL, mean corpuscular volume 73 fL, and an inappropriately low reticulocyte response. Ferritin is 7 ng/mL, transferrin saturation is low, and total iron-binding capacity is elevated. The smear shows small, pale red cells without fragments. Kidney and liver tests are normal, and the inflammatory marker is not elevated.

These results confirm iron-deficiency anemia. They do not identify the cause.

Tissue transglutaminase immunoglobulin A is clearly positive, and total immunoglobulin A is normal. The clinician explains that this raises the probability of celiac disease but is not, by itself, the complete adult diagnostic pathway. The patient continues gluten until evaluation is complete.

After shared discussion, upper endoscopy and colonoscopy are arranged. Colonoscopy finds no bleeding lesion. Upper endoscopy has no gastric ulcer, and appropriately sampled duodenal biopsies show changes consistent with celiac disease, and the gastroenterology team integrates histology, serology, symptoms, and diet history and confirms celiac disease.

The final explanation is not simply celiac disease caused everything. Celiac-related impaired absorption is the best-supported primary mechanism, while menstrual loss and lower dietary iron may add to the deficit. The negative colonoscopy reduces concern for a colonic source at this time but does not make future new bleeding or symptoms irrelevant.

Management plan#

Replace iron and treat the cause#

Iron replacement begins while the evaluation proceeds, using a formulation and schedule selected for tolerance, affordability, severity, and likely absorption. Exact dosing is omitted because product elemental-iron content, comorbidities, interactions, and the treatment plan require clinician and pharmacist review. The 2024 AGA update notes that oral iron should generally be given no more than once daily and that alternate-day use may be better tolerated for some patients. Intravenous iron is considered when oral therapy is not tolerated, stores do not improve, or absorption is unlikely to be adequate.

After celiac disease is confirmed, treatment includes a gluten-free diet with referral to a dietitian experienced in celiac disease. The team assesses nutritional deficiencies and other complications according to the gastroenterology plan. Cross-contact, label reading, cultural food patterns, cost, and access to suitable staples are addressed. A diet instruction without practical support is not a complete treatment.

The clinician reviews the need for the anti-inflammatory medicine and discusses safer headache management if gastrointestinal injury remains a concern. Medicines are not stopped or changed without considering the indication and alternatives.

Alternatives and contraindications#

• If celiac serology were negative but suspicion remained high, immunoglobulin status, gluten intake, assay performance, and the need for specialist evaluation would be reconsidered.
• If endoscopy found a bleeding lesion, management would target that source while iron is replaced.
• If hemoglobin failed to rise despite a confirmed regimen, the team would assess adherence, ongoing loss, malabsorption, the initial diagnosis, and competing causes before simply escalating iron.
• If inherited microcytosis remained plausible after repletion, hemoglobin testing could be pursued. Testing during severe iron deficiency can complicate interpretation of some results.

Iron is not given indefinitely without monitoring. Excess treatment can be harmful, and normalization of hemoglobin does not prove that iron stores or the underlying cause have been corrected.

Escalation, referral, and safety net#

Emergency evaluation is appropriate for hemodynamic instability, fainting, or chest pressure. It is appropriate for severe breathlessness, active heavy bleeding, or black stool with weakness. It is appropriate for vomiting blood, acute severe abdominal pain, or rapid clinical decline. A very low hemoglobin value is interpreted with symptoms, speed of change, cardiovascular disease, pregnancy status, and active bleeding rather than a threshold you looked up.

Prompt gastroenterology referral is appropriate for confirmed iron-deficiency anemia that warrants endoscopic evaluation. It is appropriate for positive celiac serology, alarm symptoms, or persistent gastrointestinal symptoms. It is appropriate for recurrent deficiency or lack of response. Hematology input becomes important when the diagnosis is unclear, anemia is severe or mixed, the smear is concerning, another cell line is abnormal, or response is discordant. Safety-net instructions identify what to watch for and who will review every pending result, because a positive celiac test, a pathology result, or a falling hemoglobin can be lost between office, laboratory, and specialist systems while everyone assumes you have seen it.

Communication, shared decisions, and equity#

The clinician separates three messages:

1. The blood tests confirm that iron stores are depleted.
2. Replacing iron may improve symptoms, but the team still needs to determine why iron became low.
3. Celiac testing and gastrointestinal evaluation are choices within a reasoned sequence, not evidence that cancer is assumed.

Menstrual history is discussed respectfully and specifically. The clinician does not tell the patient that anemia is normal for women. Endoscopy decisions include age, symptom pattern, and severity. They include family history, procedural risk, access, and preferences. The possibility of serious disease is explained proportionately, without using fear to force a choice.

A gluten-free diet can be expensive and socially disruptive. The plan considers household cooking, work meals, and religious and cultural foods. It considers food insecurity, insurance coverage for dietitian care, and the patient's preferred language. Teach-back checks whether she understands why gluten should continue until testing is finished and how iron will be monitored.

Follow-up and contingencies#

The team repeats the blood count and iron measures after an interval appropriate to severity and route of therapy, often within several weeks for an early response check. The exact schedule comes from the treating team. Improvement in energy is useful but cannot replace laboratory monitoring.

Follow-up asks you four separate questions:

• Is hemoglobin responding at the expected pace?
• Are iron stores being restored, not merely the hemoglobin value?
• Is the patient tolerating and taking the planned therapy?
• Has the source been treated, and is there evidence of continued loss or malabsorption?

Celiac follow-up includes symptom review, dietitian support, serologic monitoring when appropriate, and assessment of nutritional or bone-health concerns through the specialist plan. Recurrent deficiency, new bleeding, weight loss, persistent diarrhea, or an inadequate response triggers reassessment rather than automatic repetition of the same prescription.

Reasoning traps and alternative pathways#

• Stopping at the label microcytic: Cell size narrows the differential but does not prove iron deficiency.
• Stopping at low ferritin: Ferritin confirms depleted stores more readily than it explains the cause.
• Assuming menstruation is sufficient: Quantify the bleeding and keep gastrointestinal and absorption causes in proportion.
• Starting a gluten-free diet before testing: This can make serology and biopsy less reliable.
• Ordering every gastrointestinal test at once: Sequence serology, standard endoscopy, treatment response, and small-bowel testing according to risk and guidance.
• Using a negative stool blood test as clearance: Intermittent bleeding and nonbleeding lesions can be missed, and the test was not designed to replace the indicated diagnostic pathway.
• Equating symptom improvement with cure: Hemoglobin, iron stores, and the cause each need follow-up.
• Ignoring mixed causes: Celiac disease, menstrual loss, diet, and medication-related injury can coexist.

An alternative branch would emerge if ferritin were not low and inflammation were substantial. That pattern would require closer separation of iron-restricted erythropoiesis from true depletion. A very high red-cell count with lifelong microcytosis and normal iron stores would raise inherited microcytosis. Overt bleeding or instability would move the case from ambulatory sequencing to urgent stabilization and source control.

Evidence limits and what could change#

Ferritin thresholds are less reliable during inflammation, chronic kidney disease, liver disease, and some malignancies. Endoscopy recommendations differ in strength by age, menopausal status, symptoms, and evidence certainty. The AGA guideline is explicit that its recommendations do not answer every recurrent or treatment-refractory scenario.

Celiac tests depend on immunoglobulin status, gluten intake, assay performance, pretest probability, and biopsy quality. Adult confirmation practices can vary in selected circumstances and should follow current gastroenterology guidance. The case analysis ends with one coherent explanation, but real patients may have more than one source and may need a different sequence because of pregnancy, comorbidity, procedural risk, or local access.

Key points#

• Confirm both anemia and iron depletion before assigning iron deficiency, then continue to the cause.
• Menstruation changes probability but does not automatically close gastrointestinal or malabsorption reasoning.
• Celiac serology is most useful while the patient is still eating gluten and must be interpreted with immunoglobulin status.
• Iron replacement and cause-finding proceed together, with response, tolerance, and iron stores monitored separately.
• Negative initial testing reduces selected risks but does not erase new symptoms, recurrent deficiency, or a poor treatment response.