Iron & Ferritin Guide: Understanding Fatigue

Why Iron Matters

Iron is essential for producing hemoglobin—the protein in red blood cells that carries oxygen to your tissues. Without enough iron, your cells become oxygen-starved, leading to fatigue, weakness, and impaired cognitive function.

The challenge: Iron deficiency is the most common nutritional deficiency worldwide, affecting 25% of the global population—especially women of reproductive age, pregnant women, athletes, and vegetarians.

Key Iron Biomarkers Explained

Serum Iron

What it is: The amount of iron circulating in your blood at the time of the test.

Reference range: 60-170 µg/dL

The problem: Serum iron fluctuates throughout the day based on recent meals and stress. It's not a reliable standalone marker for iron status.

Ferritin (The Gold Standard)

What it is: A protein that stores iron in your cells. Ferritin reflects your total body iron reserves.

Reference range: 12-300 ng/mL (men), 12-150 ng/mL (women)

Optimal range: 50-100 ng/mL for most adults. Athletes may need higher (100-150 ng/mL).

⚠️< 15 ng/mL: Severe iron deficiency
⚠️15-30 ng/mL: Low iron stores, symptoms likely
⚠️30-50 ng/mL: Suboptimal, especially for athletes
✓50-150 ng/mL: Optimal range
⚠️> 300 ng/mL: Iron overload risk (hemochromatosis)

Important: Ferritin is an acute-phase reactant—it rises with inflammation, infection, or liver disease. If hs-CRP is elevated, ferritin may be falsely normal despite low iron stores.

TIBC (Total Iron-Binding Capacity)

What it is: Measures how much transferrin (the protein that transports iron) is available to bind iron.

Reference range: 250-450 µg/dL

Interpretation: High TIBC suggests iron deficiency (body produces more transferrin to capture scarce iron). Low TIBC may indicate chronic disease or malnutrition.

Transferrin Saturation

What it is: The percentage of transferrin saturated with iron (Serum Iron ÷ TIBC × 100).

Reference range: 20-50%

Interpretation: < 20% suggests iron deficiency. > 50% may indicate iron overload.

Symptoms of Iron Deficiency

•Fatigue and weakness: The hallmark symptom
•Pale skin and nail beds
•Shortness of breath during exercise
•Cold hands and feet
•Brain fog and difficulty concentrating
•Hair loss
•Restless leg syndrome
•Brittle nails or spoon-shaped nails (koilonychia)

Causes of Iron Deficiency

🩸 Blood Loss

Heavy menstrual periods, GI bleeding (ulcers, polyps), blood donation.

🥗 Inadequate Intake

Vegetarian/vegan diets without proper supplementation or iron-rich foods.

🤰 Increased Demand

Pregnancy, breastfeeding, rapid growth (children/teens).

🦠 Poor Absorption

Celiac disease, Crohn's disease, gastric bypass, antacid overuse.

🏃 Athletes

Endurance training increases iron loss through sweat, GI microbleeding, and red blood cell breakdown.

🔥 Chronic Inflammation

Inflammatory conditions sequester iron, making it unavailable (anemia of chronic disease).

How to Optimize Your Iron

🥩 Dietary Sources

Heme iron (animal sources—better absorbed):

•Red meat, liver (highest)
•Poultry, fish, eggs

Non-heme iron (plant sources—less absorbed):

•Lentils, beans, tofu, spinach, fortified cereals
•Pro tip: Pair with vitamin C (citrus, peppers) to enhance absorption

💊 Supplementation (When Needed)

Oral iron:

•Ferrous sulfate: 65 mg elemental iron, 2-3x daily
•Ferrous bisglycinate: Gentler on stomach, better absorbed
•Timing: Take on empty stomach with vitamin C. Avoid calcium, tea, coffee (inhibit absorption)
•Side effects: Constipation, nausea, dark stools (normal)

IV iron: For severe deficiency, malabsorption, or intolerance to oral iron.

⏱️ Timeline for Improvement

•Energy improvement: 1-2 weeks
•Hemoglobin normalization: 4-8 weeks
•Ferritin repletion: 3-6 months
•Retest ferritin after 8-12 weeks to assess progress

When to Investigate Further

⚠️Unexplained iron deficiency in men or postmenopausal women → Check for GI bleeding
⚠️Ferritin remains low despite supplementation → Malabsorption workup
⚠️Very high ferritin → Consider hemochromatosis (genetic iron overload)

Are You Tired All the Time? Check Your Iron

Medical Disclaimer