One-liner#

Iron deficiency anemia management requires identifying the underlying cause (menstrual blood loss, GI bleeding, malabsorption), repleting iron stores with oral ferrous sulfate 325 mg daily (65 mg elemental iron) or IV iron if intolerant/malabsorptive, and monitoring ferritin to goal >100 ng/mL with continued supplementation 3-6 months after hemoglobin normalizes.

Quick nav#

• Definition and epidemiology
• Pathophysiology
• Clinical presentation
• Diagnostic workup
• Treatment
• Patient education
• Prognosis and monitoring
• Special populations
• When to refer
• Smartphrase snippets
• Related pages

Definition and epidemiology#

Diagnostic criteria#

Iron deficiency anemia (IDA) diagnosis:

Iron deficiency WITHOUT anemia:

• Ferritin <30 ng/mL with normal hemoglobin
• Can cause fatigue, cognitive symptoms, restless legs
• Consider treatment if symptomatic

Ferritin interpretation caveats:

• Ferritin is an acute phase reactant—elevated in inflammation, infection, malignancy, liver disease
• In inflammatory states, ferritin <100 ng/mL suggests iron deficiency
• Transferrin saturation <20% supports iron deficiency even with “normal” ferritin

Epidemiology#

Iron deficiency is the most common nutritional deficiency worldwide, affecting ~2 billion people. In the US, IDA prevalence is 5-12% in non-pregnant women, 2% in adult men, and up to 20% in pregnant women. Premenopausal women are most commonly affected due to menstrual blood loss. In men and postmenopausal women, GI blood loss is the most common cause and requires investigation. Risk factors include heavy menstrual bleeding, pregnancy, vegetarian/vegan diet, frequent blood donation, GI conditions (celiac, IBD, gastric bypass, H. pylori), chronic NSAID use, and low socioeconomic status.

Pathophysiology#

Mechanism (clinical understanding)#

Iron is essential for hemoglobin synthesis, oxygen transport, and cellular metabolism. The body has no active excretion mechanism for iron—losses occur only through bleeding, desquamation, and (in women) menstruation.

Iron absorption: Dietary iron is absorbed in the duodenum and proximal jejunum. Heme iron (from meat) is absorbed more efficiently (15-35%) than non-heme iron (2-20%). Absorption is enhanced by vitamin C and inhibited by calcium, tannins (tea), phytates (grains), and PPIs/H2 blockers.

Iron storage and transport: Absorbed iron binds to transferrin for transport to bone marrow (for hemoglobin synthesis) and tissues. Excess iron is stored as ferritin in liver, spleen, and bone marrow. Ferritin reflects total body iron stores.

Stages of iron deficiency:

1. Iron depletion: Ferritin falls; hemoglobin normal; often asymptomatic
2. Iron-deficient erythropoiesis: Transferrin saturation falls; hemoglobin still normal; may have fatigue
3. Iron deficiency anemia: Hemoglobin falls; MCV decreases (microcytosis); symptomatic

Why symptoms occur: Reduced hemoglobin decreases oxygen-carrying capacity, causing fatigue, dyspnea on exertion, and tachycardia. Iron is also essential for myoglobin (muscle function), cytochromes (energy production), and neurotransmitter synthesis—explaining fatigue, weakness, and cognitive symptoms even before anemia develops.

Common causes by population:

• Premenopausal women: Menstrual blood loss (most common); pregnancy; inadequate intake
• Men and postmenopausal women: GI blood loss until proven otherwise (colon cancer, gastric cancer, ulcers, angiodysplasia)
• All ages: Malabsorption (celiac, gastric bypass, H. pylori, PPI use); inadequate intake (vegetarian/vegan); chronic blood donation

How to explain to patients#

Iron is a mineral your body needs to make hemoglobin—the part of red blood cells that carries oxygen from your lungs to the rest of your body. When you don’t have enough iron, your body can’t make enough healthy red blood cells, and your tissues don’t get enough oxygen.

Think of it like a delivery truck running low on fuel. The truck (your blood) can’t deliver as many packages (oxygen) to where they need to go. That’s why you feel tired, short of breath, and weak.

Your body can’t make iron—you have to get it from food or supplements. And your body can’t get rid of extra iron easily, so the main way you lose iron is through bleeding. That’s why we need to figure out where you might be losing blood, whether it’s from heavy periods, bleeding in your stomach or intestines, or another cause.

Clinical presentation#

Characteristic symptoms#

Classic anemia symptoms:

• Fatigue, weakness, low energy (most common)
• Dyspnea on exertion
• Decreased exercise tolerance
• Palpitations, awareness of heartbeat
• Dizziness, lightheadedness

Iron deficiency-specific symptoms:

• Pica (craving non-food items: ice [pagophagia], dirt, starch, clay)
• Restless legs syndrome (urge to move legs, worse at rest/night)
• Brittle nails, koilonychia (spoon-shaped nails)
• Angular cheilitis (cracks at corners of mouth)
• Glossitis (smooth, sore tongue)
• Dysphagia (Plummer-Vinson syndrome—rare)
• Hair loss

Cognitive and mood symptoms:

• Difficulty concentrating, “brain fog”
• Irritability
• Depression
• Poor memory

Symptom severity correlates with:

• Degree of anemia (Hgb level)
• Rate of onset (gradual onset better tolerated)
• Underlying cardiopulmonary reserve

Physical exam findings#

Vital signs:

• Tachycardia (compensatory; especially with exertion)
• Tachypnea with exertion
• Orthostatic hypotension (if severe)

General:

• Pallor (conjunctival, palmar creases, nail beds)
• Fatigue, listlessness

HEENT:

• Conjunctival pallor (pull down lower lid—pale pink vs red)
• Glossitis (smooth, beefy red tongue)
• Angular cheilitis (fissures at mouth corners)
• Pale oral mucosa

Cardiovascular:

• Tachycardia
• Flow murmur (systolic, usually at LUSB; due to hyperdynamic circulation)
• Bounding pulses

Nails:

• Koilonychia (spoon nails)—late finding
• Brittle, ridged nails

Neurologic:

• Restless legs (patient may report; not usually seen on exam)

Red flags#

Severe anemia requiring urgent evaluation:

• Hemoglobin <7 g/dL
• Symptomatic anemia (chest pain, dyspnea at rest, syncope, altered mental status)
• Active bleeding (melena, hematochezia, hematemesis)
• Hemodynamic instability

Concerning for malignancy:

• Men or postmenopausal women with IDA (GI malignancy until proven otherwise)
• Weight loss, anorexia
• Change in bowel habits
• Palpable abdominal mass
• Lymphadenopathy

Action: Severe symptomatic anemia → ED for possible transfusion. IDA in men/postmenopausal women → expedited GI workup.

Diagnostic workup#

Initial evaluation#

For suspected iron deficiency anemia:

Iron studies interpretation:

When ferritin is unreliable (inflammation present):

• Use ferritin <100 ng/mL as threshold for iron deficiency
• Transferrin saturation <20% supports iron deficiency
• Consider soluble transferrin receptor (sTfR) if available—elevated in iron deficiency, normal in ACD

Confirmatory testing#

Finding the cause (essential in all patients):

Premenopausal women:

• Assess menstrual history: How many days? How heavy? Clots? Flooding? Changing pads/tampons hourly?
• Heavy menstrual bleeding (>80 mL/cycle) is most common cause
• If menstrual history doesn’t explain, proceed with GI workup

Men and postmenopausal women:

• GI blood loss until proven otherwise
• Colonoscopy (colon cancer screening + evaluation)
• EGD if colonoscopy negative or upper GI symptoms
• Consider celiac serology (TTG-IgA)

Additional testing based on clinical suspicion:

When to refer for specialist workup#

GI referral:

• All men with IDA (colonoscopy + consider EGD)
• All postmenopausal women with IDA
• Premenopausal women with IDA not explained by menstrual loss
• Positive FIT/guaiac
• GI symptoms (abdominal pain, change in bowel habits, dysphagia)
• Failed response to iron therapy

Hematology referral:

• Severe anemia (Hgb <7) requiring transfusion consideration
• Anemia not responding to iron therapy after 4-8 weeks
• Unclear diagnosis (mixed picture, hemolysis suspected)
• Recurrent IDA despite adequate treatment and no identified cause

GYN referral:

• Heavy menstrual bleeding requiring evaluation/treatment
• Menorrhagia not responding to medical management

What NOT to order#

• Bone marrow biopsy: Rarely needed; ferritin is sufficient for diagnosis in most cases
• Serum iron alone: Varies with meals, time of day; not reliable without TIBC
• Hemoglobin electrophoresis: Only if thalassemia suspected (microcytosis with normal iron studies)
• B12/folate: Only if macrocytic or normocytic anemia, or neurologic symptoms
• Extensive workup before trial of iron: In young women with heavy menses and classic IDA, can treat empirically and reassess

Treatment#

Goals of therapy#

Primary goals:

• Normalize hemoglobin: >12 g/dL (women), >13 g/dL (men)
• Replete iron stores: Ferritin >100 ng/mL (some target >200 ng/mL)
• Resolve symptoms: Fatigue, dyspnea, pica, restless legs
• Identify and treat underlying cause

Timeline expectations:

• Reticulocyte count increases in 7-10 days
• Hemoglobin increases ~1 g/dL every 2-3 weeks
• Hemoglobin normalizes in 6-8 weeks
• Iron stores replete in 3-6 months after hemoglobin normalizes

Non-pharmacologic management#

Dietary optimization:

• Increase heme iron sources: Red meat, poultry, fish, shellfish (best absorbed)
• Non-heme iron sources: Fortified cereals, beans, lentils, spinach, tofu
• Enhance absorption: Take iron with vitamin C (orange juice, tomatoes)
• Avoid absorption inhibitors with iron: Coffee, tea, calcium, dairy, antacids

Dietary iron alone is usually insufficient to correct IDA—supplementation required.

Address underlying cause:

• Treat heavy menstrual bleeding (hormonal therapy, IUD, etc.)
• Treat H. pylori if present
• Gluten-free diet if celiac disease
• Discontinue NSAIDs if causing GI blood loss
• Optimize PPI use (can impair absorption)

Pharmacologic management#

Oral iron - First-line therapy:

Oral iron prescribing pearls:

• Every-other-day dosing is now preferred: Recent evidence shows better fractional absorption and fewer side effects
• Start with one dose daily: Can increase if tolerated, but more is not always better
• Take on empty stomach for best absorption (1 hour before or 2 hours after meals)
• If GI intolerant: Take with small amount of food, switch to every-other-day, try different formulation
• Vitamin C enhances absorption: 200 mg vitamin C with each dose
• Separate from interfering substances by 2 hours: PPIs, antacids, calcium, dairy, coffee, tea
• Warn about side effects: Constipation, nausea, dark stools, metallic taste
• Duration: Continue 3-6 months AFTER hemoglobin normalizes to replete stores

IV iron - When oral fails or inappropriate:

IV iron indications:

• Oral iron intolerance (persistent GI side effects despite formulation changes)
• Malabsorption (celiac, gastric bypass, IBD)
• Ongoing blood loss exceeding oral replacement capacity
• Severe anemia (Hgb <7) needing rapid repletion
• CKD on ESA therapy
• Inflammatory conditions where oral iron ineffective
• Patient preference for faster repletion

Blood transfusion:

• Reserve for severe symptomatic anemia (Hgb <7 with symptoms) or hemodynamic instability
• Transfuse 1 unit at a time; reassess after each unit
• Goal is symptom relief, not normal hemoglobin
• Each unit raises Hgb ~1 g/dL

Patient counseling points#

For oral iron:

• “Take your iron pill on an empty stomach if you can—it absorbs better. If it upsets your stomach, you can take it with a small amount of food.”
• “Taking it with orange juice or vitamin C helps your body absorb more iron.”
• “Don’t take it at the same time as your calcium, antacids, or with coffee or tea—wait at least 2 hours.”
• “Your stools will turn dark or black—this is normal and expected. But if you see red blood or tarry black stools, call us.”
• “Constipation is common. Drink plenty of water and eat fiber. We can add a stool softener if needed.”
• “It takes 2-3 months to get your blood count back to normal, and then you need to keep taking iron for another 3-6 months to refill your body’s iron stores.”
• “Don’t stop taking it just because you feel better—your stores need time to refill.”

For IV iron:

• “We’re giving you iron through your vein because your body isn’t absorbing the pills well enough (or you can’t tolerate them).”
• “The infusion takes about 15-30 minutes. We’ll monitor you during and after for any reactions.”
• “You might feel some flushing, mild nausea, or muscle aches—these usually pass quickly.”
• “Serious reactions are rare, but tell the nurse right away if you feel short of breath, dizzy, or have chest tightness.”

Monitoring and follow-up#

After starting oral iron:

• CBC and reticulocyte count at 2-4 weeks (reticulocytes should increase; Hgb should start rising)
• CBC and ferritin at 8 weeks (Hgb should be improving; ferritin rising)
• Continue iron until ferritin >100 ng/mL (typically 3-6 months after Hgb normalizes)

After IV iron:

• CBC at 4 weeks (expect significant Hgb improvement)
• Ferritin at 8-12 weeks (will be elevated immediately post-infusion; wait to recheck)

If not responding to oral iron (Hgb not increasing by 1 g/dL in 4 weeks):

1. Assess adherence and proper administration
2. Consider malabsorption (celiac, H. pylori, PPI effect)
3. Consider ongoing blood loss exceeding replacement
4. Consider switching to IV iron
5. Reconsider diagnosis (thalassemia, anemia of chronic disease)

Patient education#

What is this condition?#

Iron deficiency anemia means your body doesn’t have enough iron to make healthy red blood cells. Red blood cells carry oxygen from your lungs to the rest of your body. When you don’t have enough of them, or they’re too small, your body doesn’t get enough oxygen.

This makes you feel tired, weak, and short of breath, especially when you’re active. You might also notice your heart beating fast, feel dizzy, or have trouble concentrating.

Iron deficiency happens when you lose more iron than you take in. The most common reasons are heavy menstrual periods in women, or bleeding somewhere in your digestive system (stomach or intestines) in men and older women. Sometimes it’s because your body isn’t absorbing iron well from food.

What you can do#

Take your iron supplement exactly as prescribed. For most people, this means once a day on an empty stomach, or every other day if it upsets your stomach.

Take your iron with a glass of orange juice or a vitamin C tablet—this helps your body absorb more iron.

Avoid taking iron at the same time as calcium supplements, antacids, coffee, or tea. These can block iron absorption. Wait at least 2 hours between them.

Eat iron-rich foods: red meat, chicken, fish, beans, lentils, fortified cereals, and dark leafy greens. Cooking in cast iron pans can add iron to your food.

Expect your stools to turn dark green or black—this is normal and means the iron is working.

If you get constipated, drink more water, eat more fiber, and ask us about a stool softener.

When to seek care#

Call your doctor if you have blood in your stool (red or black tarry stools), vomit blood, or have severe stomach pain.

Call if you feel much more tired than usual, have chest pain, feel your heart racing, or feel faint.

Call if you’re not feeling better after 4-6 weeks of taking iron, or if your symptoms are getting worse.

Go to the emergency room if you have severe shortness of breath, chest pain, or feel like you might pass out.

Questions to ask your doctor#

• What is causing my iron deficiency?
• Do I need any tests to find out why I’m losing iron?
• How long will I need to take iron supplements?
• What should my hemoglobin and ferritin levels be?
• Should I take iron every day or every other day?
• What if I can’t tolerate the iron pills?
• When should I get my blood checked again?

Prognosis and monitoring#

Expected course#

With treatment:

• Reticulocyte count increases within 7-10 days (first sign of response)
• Symptoms (fatigue, dyspnea) improve within 2-4 weeks
• Hemoglobin increases ~1 g/dL every 2-3 weeks
• Hemoglobin normalizes in 6-8 weeks
• Iron stores (ferritin) replete in 3-6 months after hemoglobin normalizes
• Pica and restless legs often resolve within days to weeks

Without treatment:

• Progressive anemia with worsening symptoms
• Cardiovascular compensation (tachycardia, high-output state)
• Eventually: heart failure, angina, cognitive impairment
• In pregnancy: increased risk of preterm birth, low birth weight, maternal mortality

Recurrence:

• Common if underlying cause not addressed
• Premenopausal women may need ongoing supplementation if heavy menses continue
• GI blood loss requires treatment of source

Monitoring parameters#

Complications to watch for#

Treatment-related:

• GI side effects from oral iron (constipation, nausea, abdominal pain)
• Iron overload (rare with oral; possible with repeated IV infusions without monitoring)
• Infusion reactions with IV iron (rare; usually mild)

Disease-related:

• Missed GI malignancy (always investigate cause in men and postmenopausal women)
• Recurrent anemia if cause not addressed
• Cardiovascular complications if severe/prolonged (high-output heart failure)

Monitoring for iron overload:

• Not a concern with oral iron in iron-deficient patients
• With repeated IV iron: check ferritin before each course; hold if >500 ng/mL
• Symptoms of overload: joint pain, fatigue, abdominal pain, bronze skin (rare)

Special populations#

Elderly/geriatric#

Presentation differences:

• May present with falls, confusion, or worsening heart failure rather than classic symptoms
• Fatigue often attributed to aging
• Higher prevalence of GI malignancy as cause

Workup:

• Lower threshold for GI evaluation (colonoscopy, EGD)
• Consider malignancy, malabsorption, poor nutrition
• Check B12 (often coexists)

Treatment:

• Oral iron generally well-tolerated
• Start with lower doses if GI-sensitive
• IV iron safe and effective if oral not tolerated
• Transfusion threshold: Hgb <7-8 g/dL or symptomatic

Beers criteria:

• Iron supplements not on Beers list
• Avoid excessive iron (ferritin >300) due to theoretical oxidative stress concerns

Polypharmacy considerations:

• Review for drug interactions affecting iron absorption (PPIs, H2 blockers, calcium, antacids)
• Multiple medications may contribute to GI blood loss (NSAIDs, anticoagulants, antiplatelet agents)
• Simplify regimen when possible—consider every-other-day dosing for better adherence

Chronic kidney disease#

Unique considerations:

• Functional iron deficiency common (adequate stores but can’t mobilize for erythropoiesis)
• Often on ESAs (erythropoietin-stimulating agents) which increase iron demand
• Oral iron poorly absorbed in CKD
• IV iron preferred in CKD stages 4-5 and dialysis

Targets in CKD:

• Ferritin >100 ng/mL (>200 if on ESA)
• Transferrin saturation >20%
• Higher ferritin targets (200-500) if on ESA therapy

Treatment:

• IV iron preferred (iron sucrose, ferric carboxymaltose)
• Oral iron can be tried in earlier CKD stages
• Coordinate with nephrology for ESA management

Other populations#

Pregnancy:

• Iron requirements increase dramatically (from 1 mg/day to 6 mg/day in 3rd trimester)
• Screen all pregnant women for anemia
• Treat IDA aggressively—associated with preterm birth, low birth weight
• Oral iron first-line; IV iron safe in 2nd and 3rd trimesters
• Target Hgb >11 g/dL in 1st and 3rd trimesters, >10.5 g/dL in 2nd trimester
• Coordinate with OB

Inflammatory bowel disease:

• High prevalence of IDA (blood loss + malabsorption)
• Oral iron may worsen GI symptoms and inflammation
• IV iron often preferred
• Coordinate with GI

Gastric bypass/bariatric surgery:

• Malabsorption of iron (bypassed duodenum)
• Lifelong supplementation usually required
• IV iron often needed
• Monitor ferritin annually

Heart failure:

• Iron deficiency (even without anemia) worsens HF symptoms and outcomes
• IV iron (ferric carboxymaltose) improves symptoms and reduces hospitalizations
• Treat if ferritin <100 or ferritin 100-300 with transferrin sat <20%
• Coordinate with cardiology

Celiac disease:

• IDA may be presenting symptom
• Gluten-free diet improves absorption
• May need IV iron initially; oral iron effective once gut heals

Heavy menstrual bleeding:

• Most common cause in premenopausal women
• Treat anemia AND address bleeding
• Options: hormonal contraceptives, tranexamic acid, IUD, endometrial ablation, hysterectomy
• Coordinate with GYN

When to refer#

Specialist referral criteria#

GI referral (colonoscopy/EGD):

• All men with IDA
• All postmenopausal women with IDA
• Premenopausal women with IDA not explained by menstrual loss
• Positive FIT or guaiac
• GI symptoms (abdominal pain, change in bowel habits, dysphagia, weight loss)
• IDA not responding to iron therapy
• Recurrent IDA after successful treatment

Hematology referral:

• Severe anemia (Hgb <7) requiring transfusion consideration
• Anemia not responding to iron therapy after 4-8 weeks
• Unclear diagnosis (mixed picture, hemolysis suspected)
• Recurrent IDA despite adequate treatment and no identified cause
• Suspected thalassemia or other hemoglobinopathy

GYN referral:

• Heavy menstrual bleeding requiring evaluation
• Menorrhagia not responding to medical management
• Consideration of procedural intervention (ablation, IUD, hysterectomy)

Infusion center/hematology:

• IV iron administration
• Patients requiring repeated IV iron courses

Urgency levels#

Smartphrase snippets#

Iron deficiency anemia, new diagnosis: Iron deficiency anemia: Hgb [X], ferritin [X]. Etiology: [heavy menses / GI blood loss / malabsorption]. Starting ferrous sulfate 325 mg daily with vitamin C. Recheck CBC and ferritin in 8 weeks.

Iron deficiency anemia, follow-up improving: IDA follow-up on oral iron. Hgb improved from [X] to [X], ferritin [X]. Continue iron until ferritin >100 ng/mL. Recheck in [8-12 weeks].

Iron deficiency anemia, IV iron referral: IDA requiring IV iron due to [oral intolerance / malabsorption / severe anemia]. Referring for ferric carboxymaltose infusion. Recheck CBC in 4 weeks post-infusion.

Related pages#

• Fatigue (complaint) — fatigue workup including anemia evaluation
• GI Bleed (complaint) — evaluation of GI blood loss
• Chronic Kidney Disease (problem) — iron management in CKD
• Heart Failure (problem) — iron deficiency in heart failure
• Hypothyroidism (problem) — another common cause of fatigue