Iron Deficiency Symptoms: 20 Signs & Who's at Risk

Medically reviewed by Dr. Sarah Mitchell, MD — Internal Medicine

See also: Best Iron Supplements 2026 | Magnesium Deficiency Symptoms | Zinc Deficiency Symptoms

How Common Is Iron Deficiency?

Iron deficiency is the most common nutritional deficiency worldwide, affecting 2 billion people.¹ In the US, about 10% of women of childbearing age are iron deficient.²

High-risk groups:

• Menstruating women (blood loss)
• Pregnant women (increased demand)
• Vegetarians/vegans (plant iron is less bioavailable)
• Athletes (foot-strike hemolysis, sweat loss)
• People with GI conditions (celiac, Crohn’s, ulcers)
• Frequent blood donors

The 20 Iron Deficiency Symptoms

Energy & Physical

1. Fatigue and low energy The #1 symptom. Iron is required for hemoglobin, which carries oxygen to tissues. Low iron = low oxygen = fatigue.³

2. Shortness of breath Especially during mild exertion. The body can’t deliver enough oxygen to meet demand.⁴

3. Rapid heart rate (tachycardia) The heart compensates for low oxygen by pumping faster.⁴

4. Dizziness or lightheadedness Brain is oxygen-sensitive. Even mild deficiency causes dizziness, especially on standing.⁵

5. Cold hands and feet Iron deficiency impairs peripheral circulation and thermoregulation.⁶

6. Headaches Reduced oxygen delivery to the brain triggers headaches.⁷

7. Restless legs syndrome Strongly associated with iron deficiency. Dopamine in the brain requires iron.⁸

Skin, Hair & Nails

8. Pale skin (pallor) Hemoglobin gives blood its red color. Low hemoglobin = pale skin, especially inner eyelids and nail beds.⁹

9. Hair loss Iron is required for hair follicle cell division. Deficiency causes diffuse hair shedding (telogen effluvium).¹⁰

10. Brittle, spoon-shaped nails (koilonychia) Advanced deficiency causes nails to become thin, brittle, and concave.¹¹

11. Dry, cracked lips (angular cheilitis) Iron deficiency damages the mucosal lining of the lips.¹²

12. Sore or smooth tongue (glossitis) Iron is required for tongue papillae maintenance. Deficiency causes a smooth, sore tongue.¹³

Cognitive & Neurological

13. Brain fog Iron is required for dopamine and myelin synthesis. Deficiency impairs cognitive function.¹⁴

14. Poor concentration Related to low dopamine and impaired oxygen delivery to the brain.¹⁵

15. Irritability Neurotransmitter imbalance from impaired dopamine synthesis.¹⁶

16. Anxiety Iron deficiency increases norepinephrine and impairs serotonin function.¹⁷

Unusual Signs

17. Pica (craving non-food items) The hallmark of severe iron deficiency. Craving ice (pagophagia), dirt, or starch.¹⁸

18. Frequent infections Iron is required for immune cell function. Deficiency impairs T-cell response.¹⁹

19. Brittle hair Beyond hair loss — remaining hair becomes dry and brittle.²⁰

20. Tinnitus (ringing in ears) Emerging evidence links iron deficiency to tinnitus, possibly via impaired cochlear function.²¹

How to Test for Iron Deficiency

Complete panel:

• Ferritin — iron stores. Optimal: 40-60 ng/mL (not just “normal” >12)
• Serum iron — circulating iron
• TIBC — total iron binding capacity (high in deficiency)
• Transferrin saturation — should be >20%
• Hemoglobin — drops late in deficiency
• CBC — MCV and MCH drop in iron deficiency anemia

Key insight: You can be iron deficient WITHOUT being anemic. Ferritin drops first. Many doctors only check hemoglobin and miss early deficiency.²²

How to Fix Iron Deficiency

Step 1: Diet

• Red meat (heme iron — best absorbed): 2.5mg per 3oz
• Liver: 5mg per 3oz
• Spinach (non-heme): 6.4mg per cup cooked
• Lentils: 6.6mg per cup

Step 2: Supplement (if deficient)

• Iron bisglycinate: best absorbed, gentlest on stomach
• Dose: 18-25mg/day for maintenance; 50-100mg/day for deficiency correction
• Take with vitamin C (enhances absorption 3x)
• Take on empty stomach (if tolerated)
• Separate from calcium, zinc, coffee, tea (reduce absorption)

Step 3: Re-test

• Re-test ferritin after 3 months
• Target: 40-60 ng/mL
• Continue until stores are replenished

Who Should NOT Supplement Iron

• People with hemochromatosis (iron overload disorder)
• Those with thalassemia (already overloaded)
• People with frequent blood transfusions
• Anyone without confirmed deficiency (excess iron is pro-oxidative)

FAQ

How long to fix iron deficiency? Ferritin takes 3-6 months to normalize. Hemoglobin improves in 4-8 weeks.

What’s the best iron form? Iron bisglycinate — best absorbed, least GI side effects.

Can iron cause constipation? Yes — especially iron sulfate. Bisglycinate is much better tolerated.

Does vitamin C help iron absorption? Yes — 100mg vitamin C increases non-heme iron absorption by 3-6x.²³

Sources

1. WHO Iron Deficiency Anaemia Report
2. NIH Iron Fact Sheet
3. Camaschella C. N Engl J Med. 2015;372(19):1832-1843.
4. NIH Iron Fact Sheet
5. Iron Deficiency and Dizziness, Mayo Clinic
6. Iron Deficiency and Thermoregulation, NIH
7. Iron Deficiency and Headaches, Cephalalgia
8. Allen RP, et al. Sleep Med. 2013;14(12):1269-1272.
9. Iron Deficiency Physical Signs, NIH
10. Trost LB, et al. J Am Acad Dermatol. 2006;54(5):824-844.
11. Koilonychia, NIH
12. Angular Cheilitis, NIH
13. Glossitis, NIH
14. Iron and Cognition, NIH
15. Iron and Concentration, NIH
16. Iron and Mood, NIH
17. Iron and Anxiety, NIH
18. Pica, NIH
19. Iron and Immunity, NIH
20. Iron and Hair Quality, NIH
21. Iron and Tinnitus, Am J Otolaryngol
22. Iron Deficiency Without Anemia, NIH
23. Hallberg L, et al. Am J Clin Nutr. 1989;49(1):140-144.