Iron Deficiency: 30 Hidden Signs & Symptoms

By: Dr. Baker (ND)

Iron does much more than simply build red blood cells—it moves oxygen, powers enzymes, and keeps nerves firing. When iron drifts too low problems can surface in places you might not expect. The most common complication is anemia, which can lead to a wide range of symptoms. Most of the research below looks at the risk of conditions related to a marker called ferritin, a protein in the body that stores iron and releases it when needed, regulating iron availability in the body.

How Common is Iron Deficiency?

Iron imbalances are very common worldwide. A 2023 study in younger women aged 12-21 found 39% were iron deficient. In this study, 77% of women had suboptimal iron levels. About 40% of children between 6 and 59 months have anemia - a complication of low iron (World Health Organization (WHO)).

What is Iron Used For?

Iron is a key mineral your body needs to make hemoglobin, the protein in red blood cells that carries oxygen from your lungs to every part of your body. If levels drop too low it can lead to anemia.

Why Iron Deficiencies Are Often Missed

Ferritin is more than a storage tank for iron—it is also a positive acute‑phase protein, meaning its blood level climbs whenever the body senses inflammation or tissue injury [Gulhar 2023].  That surge can mislead clinicians into thinking iron reserves are plentiful when they are not.

Even small stresses distort the picture.  In Swedish teens, a simple upper‑respiratory infection doubled median ferritin within three weeks [Hulthén 1998].  Long‑lasting “silent” inflammation has the same effect: studies show ferritin runs high in obesity and metabolic syndrome, independent of true iron status [Cámara‑Gómez 2015] and in non‑alcoholic fatty‑liver disease [Wang 2017].  Heavy alcohol use or liver damage can inflate readings as ferritin leaks from injured liver cells [Litten 2009].  In autoimmune disorders such as rheumatoid arthritis, ferritin often sits in the normal‑to‑high range while other iron markets arelow—a pattern called functional iron deficiency driven by the iron‑locking hormone hepcidin [Weiss 2017].  Pregnancy shows a similar danger: relying on ferritin alone missed almost one‑third of women who developed iron deficiency by the third trimester in a 2024 prospective study [McCarthy 2024].

Because ferritin is so easy to misread, our clinic will run a full iron panel to get a comprehensive view of iron status. Putting these clues together keeps treatment on target.  Ferritin alone can fool both patients and practitioners.  A complete iron panel cuts through the noise, ensuring iron therapy is given when needed and withheld when it isn’t.

30 Hidden Signs & Symptoms:

1. Headaches & Migraines

Migraine sufferers with iron‑deficiency recorded more frequent and intense attacks (Singh 2023), while women in the top tier of dietary iron intake reported fewer migraine days overall (Meng 2021).

2. Brain Fog & Cognition

Teenagers with iron‑deficiency anemia performed worse on memory and processing tasks (Yeboah 2024). Among adults, lower ferritin predicted slower thinking speed (Rosell‑Díaz 2024), whereas higher ferritin was linked to sharper overall cognition in a large community cohort (Anjum 2020).

3. Attention‑Deficit/Hyperactivity (ADHD)

Meta‑analysis shows children with ADHD tend to have lower ferritin (Tan 2011), and field studies link lower ferritin to higher hyperactivity scores (Oner 2012). Emerging models suggest iron’s influence on dopamine may underlie these findings (Konofal 2016).

4. Sleep, Insomnia & Restless Legs

Iron‑deficiency in rheumatoid arthritis correlated with restless legs and poor sleep quality (Song 2021). Older adults with the lowest ferritin logged more nighttime leg movements (Seppi 2015), and parent‑reported sleep troubles in ADHD children paralleled low ferritin (Abdel‑Maksoud 2013). Similar links surface in autism, where lower ferritin predicted sleep fragmentation (Glickman 2013).

5. Depression

Iron is a key ingredient in making dopamine and serotonin, the brain’s “feel‑good” messengers. A 2020 study found 43% higher risk of depression in those with anemia (Lee 2024).

6. Anxiety

A large health‑database study found that people with low ferritin had about a 50 percent higher risk of anxiety (Lee 2020). Genetic studies strengthen the link, showing that being born with genes for lower iron makes anxiety more likely (Yin 2024).

7. Ear Infections

The middle ear needs iron‑powered immune cells to fight germs. Adults with stubborn otitis media were over fifteen times more likely to be iron‑deficient than healthy peers—making a simple ferritin test a smart add‑on for repeat ear infections (Cao 2024).

8. Nerve Issues

Iron keeps the myelin “insulation” around nerves healthy. In iron‑deficient children, just three months of iron therapy sped nerve signals back to normal—and sometimes even faster—highlighting iron’s role in clear sensation and steady muscle control (Kabakus 2002).

9. Restless Legs Syndrome (RLS)

Low brain iron is a well‑known trigger for the nightly urge to move your legs. A 2023 meta‑analysis showed that raising low ferritin eases RLS symptoms (Li 2023).

10. Fatigue

Low iron may cause anemia, which can lead to fatigue. However, new research suggests that even without anemia, low iron may lead to fatigue. A 2003 study (Verdon et al., 2003) was completed on women with low iron, unexplained fatigue, and an absence of anemia. It found iron supplementation led to a 29% reduction in fatigue.

11. Balance & Vertigo

Even your inner ear’s balance crystals seem iron‑sensitive. A 2024 clinic study reported that people with low ferritin were more likely to develop benign paroxysmal positional vertigo—a condition that causes a chronic spinning sensation (Bener 2024).

12. Lungs

Low iron means less hemoglobin to ferry oxygen. In chronic lung conditions, that shortage can intensify breathlessness and fatigue—the very symptoms many patients are already struggling with (Sarkar 2015). Checking ferritin can reveal whether shortness of breath is partly an “iron issue,” not just a lung issue.

13. Fibromyalgia Pain

Low iron raised the odds of fibromyalgia more than six‑fold and tracked with heavier fatigue scores, underscoring iron’s role in pain‑modulating neurotransmitters (Ortancil 2010).

14. Chronic Hives (Urticaria)

Refractory hives often improved or cleared when hidden iron‑deficiency was corrected, hinting that adequate iron tempers mast‑cell overactivity (Guarneri 2014).

15. Dental Cavities

Children with severe cavities were significantly more likely to have low iron (Atri 2023); another study found iron‑deficiency anemia was six times more common in kids with tooth decay (El‑Dentiste 2021).

16. Scleroderma & Breathlessness

A documented case showed pulmonary pressures and shortness of breath in systemic sclerosis reversed after intravenous iron normalised ferritin (Neumann 2022). Surveys also indicate iron‑deficiency is more frequent in scleroderma and may worsen breathlessness.

17. Concussion & TBI

Hospital data reveal that anemia at admission predicts poorer recovery after traumatic brain injury (Liao 2016).

18. Heart Failure & Cardiovascular Risk

Iron‑deficiency anemia remains under‑treated in heart‑failure clinics despite its high prevalence (Taha 2024) and its association with worse outcomes (Berton 2024; Ahmed 2023). Community data show older adults with low ferritin develop heart failure more often (Sakai 2024), while a landmark cohort found both very low and very high ferritin carry risk (Silvestre 2017).

19. Hidradenitis Suppurativa (HS)

HS is a chronic inflammatory skin condition. Patients with HS were found to have 40 percent lower ferritin and transferrin saturation, suggesting iron may be related to inflammation (Matusiak 2020). In broader inflammatory cohorts, correcting anemia reduced C‑reactive protein, hinting iron repletion could calm HS‑related inflammation (Auerbach 2019).

20. Gallstones

Analysis of ultrasound surveys linked low serum iron to higher gallstone prevalence, perhaps via slower bile acid synthesis (Sharma 2008).

21. Lichen Planus

Oral‑cavity biopsies revealed iron‑deficiency more often in lichen‑planus patients than in controls (Khan 2015).

22. High Cholesterol

Epidemiology shows iron‑deficiency anemia correlates with higher LDL cholesterol (Sehgal 2011).

23. Tonsillitis

Children with recurrent tonsillitis were significantly more likely to have low ferritin, pointing toward iron as an immune‑modulating cofactor (Ozturk 2016).

24. Asthma

Higher ferritin levels (within the normal range), were linked to lower risk of asthma attacks (Han 2015).

25. Longevity & General Health

A large English cohort showed a relationship with longevity over 7.7 years of follow‑up (Kadoglou 2017). Staying in the mid‑range appears most compatible with a long, healthy life.

26. Osteoporosis

Bone likes iron in moderation. In >10 000 adults, both very low and very high ferritin raised osteoporosis risk, whereas mid‑range iron (alongside manganese, copper, selenium) protected bone density (Wei 2022).

27. Women’s Fertility

In a fertility‑clinic case‑control, women with unexplained infertility were three times more likely to have low ferritin (Holzer 2023).

28. Mood & Depression

A meta‑analysis of 14 studies (10 764 cases) found anemia raised depression odds by 43 % (Lee 2020). Iron helps synthesize dopamine and serotonin, both of which play a role in mood.

29. Hair Loss

Dermatology clinics often check ferritin for unexplained hair loss because iron is a growth co‑factor for hair. In a cross‑sectional study of 554 non‑anemic women, those with low ferritin were more than twice as likely to report recent hair loss—an odds ratio of 2.26—even when anemia was not present (Beatrix 2022).

30. Muscle Cramps

Low iron can lead to anemia, which means less oxygen to the muscles. This can lead to muscle pain and cramps (Merck).

Biology of Iron

Key functions Iron is essential for:

• Oxygen transport, as part of hemoglobin in red blood cells;

• Energy production, in mitochondrial enzymes of the electron-transport chain;

• Immune defense, where iron availability affects white-blood-cell function and helps restrict pathogens.

Heme vs. non-heme iron

• Heme iron (from meat, fish, poultry) is bound within a porphyrin ring and absorbed intact (15–35 % uptake) via a dedicated transporter.

• Non-heme iron (from plants, supplements) exists as Fe³⁺ or Fe²⁺; only 1–10 % is absorbed and its uptake is boosted by vitamin C and inhibited by phytates, polyphenols, and calcium.

Causes of Low Iron

While iron deficiency commonly occurs when intake is too low, it may develop even when people are eating enough iron. Other factors can affect iron absorption such as genetics, medication use, and other health conditions. Chronic blood loss can also be a factor. Heavy menstrual periods, ulcers, or colon problems can cause small but steady blood loss that drains iron stores over time.

Over‑Active Thyroid

A study found that untreated hyperthyroidism distorts iron markers; ferritin often rises while usable iron falls, normalising only after thyroid hormones are controlled (Kubota 1993).

Proton‑Pump Inhibitors (PPIs)

Long‑term use of acid‑blocking PPIs can hinder iron absorption.

Gut Inflammation: Inflammatory Bowel Disease (IBD)

Blood tests found 39% of IBD patients carried at least one deficiency, with iron topping the list (Park 2021). Intriguingly, blood samples collected years before diagnosis already showed lower ferritin in future IBD cases (Widbom 2020), hinting that iron depletion may precede (and perhaps aggravate) gut inflammation.

Stomach & Esophagus

Persistent acid reflux (GERD) can irritate the food pipe and cause tiny, hidden bleeds. Over time, that slow blood loss drains your iron reserves, explaining why people with chronic GERD are far more likely to become iron‑deficient (Lupu 2022).

Forms of Iron

Iron supplements come in different chemical forms that change how well the body uses them. Here are important difference between them:

• How much is absorbed: Some forms dissolve easily and deliver more iron into the blood, helping make red blood cells.

• Stomach comfort: Some types can cut down on upset stomach, nausea, or constipation.

Picking the proper form boosts iron levels more effectively and makes sticking with treatment easier.

Practical Takeaways

• Test, don’t guess: our clinic tests five different iron markers to give a comprehensive view of iron levels.

• Aim mid‑range: Too little can lead to deficiency; too much may accumulate and overload the body. 

• Monitor: If supplementing, it is important to re‑test every 8–12 weeks

In naturopathic medicine, we also look beyond just lab numbers. By exploring factors like diet, digestion, and other factors, we aim to find and treat the underlying reasons behind low or high iron, and support the whole person, not just the test results. Studies show that even within the “normal” range people may still be symptomatic. Instead of reaching a minimum, we aim to reach optimal iron levels for optimal health. Reach out if you are interested in comprehensive iron testing & testing related to other conditions. This is one of over 2,000 medical tests that our clinic has access to. We have over 120 custom built blood test panels designed by our naturopaths and backed by over 1,000 studies conducted by more than 6,000 research authors worldwide. For the rest of this post & posts on 60 other conditions see: https://www.simcoenaturopathic.ca/