Iron, Inflammation & the Hidden Link to Fatigue: Why More Isn’t Always Better

Iron deficiency is widely discussed in women’s health — and for good reason. Many women truly need support with low iron, especially during their reproductive years.

But there’s another side to the story that often gets overlooked: more iron isn’t always better. Excess iron — particularly from over-supplementation — can quietly drive inflammation, disrupt the gut microbiome, and contribute to deep fatigue.

This slower transit can lead to constipation, fullness, and abdominal distension, especially when hormones, hydration or stress levels are off balance. The result is the familiar bloating many women experience before their period. Supporting digestion during this phase can make a big difference in comfort and overall wellbeing.

As a clinician I work with women who are struggling with SIBO or IBS type symptoms. They also have been taking high doses of iron recommended to them because their ferritin was low normal and they were experiencing fatigue. Once we support their iron recycling system (yes your body recycles iron, more on this later) they reduce supplementation and their gut symptoms improve.

Understanding this less-discussed side of iron can be empowering, especially if you’ve been taking supplements but still don’t feel well.

Iron: A Nutrient… and a Growth Factor for Bacteria

Iron is essential for energy production, oxygen transport, and immune function. But in the microbial world, it’s also highly prized. Many bacteria rely on iron to grow, reproduce, and become more virulent.

Too much free iron in the gut or bloodstream can shift the microbial ecosystem in the wrong direction:

How excess iron contributes to dysbiosis:

Iron supplements leave unabsorbed iron in the gut.
Opportunistic or pathogenic bacteria feed on this iron, while beneficial bacteria (like Lactobacillus) do not.
Over time, this can lead to bloating, gas, constipation or loose stools, gut inflammation, recurrent infections, and worsening fatigue.

For women already dealing with gut imbalance, IBS-like symptoms, or recurrent thrush/UTIs, unnecessary iron supplementation can exacerbate the problem.

The body knows this — one of our key iron-regulating hormones, hepcidin, rises during infection and inflammation to withhold iron from pathogens. Supplements bypass this natural protective mechanism.

Iron as a Pro-Inflammatory Molecule

Excess iron, especially in its free or unbound form, is highly reactive and can generate oxidative stress — essentially, cellular rusting.

This oxidative stress can:

Damage cell membranes
Irritate the gut lining
Trigger immune activation
Add load to the liver
Disrupt hormonal balance
Promote chronic, low-grade inflammation

This can manifest as symptoms that don’t always make sense: fatigue, brain fog, achy muscles, feeling “inflamed,” worsening PMT or cycle symptoms, trouble recovering from exercise, or poor stress tolerance.

Most importantly, iron overload can stress your mitochondria, the energy factories inside your cells.

Women’s Health & the Iron Mismatch
Many of us self prescribe iron based on symptoms like fatigue, dizziness, or brain fog — often without full iron studies, or without investigating whether fatigue is actually due to:

Gut dysfunction
Chronic stress
Poor sleep
Inflammation
Hormonal imbalance
Overtraining
Nervous system dysregulation

If iron isn’t the root cause, supplementing it won’t restore energy — and in some cases, may worsen underlying inflammation.

How to Support Iron Safely & Holistically

Here are some principles I teach my clients:

Test — don’t guess.
Minimum labs: ferritin, serum iron, transferrin saturation, CRP (inflammation marker can artificially elevate ferritin). Understand that a menstruating's women optimal ferritin is between 30-50 ng/ml. If your ferritin is sitting at 50 that is high normal.
Support the gut first.
A healthy gut improves absorption naturally and reduces the risk of dysbiosis when iron is used.
Reduce inflammation & regulate the nervous system.
Stress and inflammation directly suppress iron absorption and distort iron metabolism.
Use food-based iron where possible.
Especially for women on the lower but not deficient end.
Supplement only when clinically appropriate.
Ideally with gentle, well-absorbed forms under guidance. Take ever other day and if its not working, that doesn’t mean you need to increase your dosage necessarily.
Balance your minerals holistically.
Your body has the essential co factors to absorb and regulate iron metabolism. Metals like copper help to make important proteins that regulate iron called ceruloplasmin.

The Takeaway

Iron is essential — but balance matters. Both too little and too much create real health challenges.

If you’ve been:

Taking iron and not feeling better
Experiencing new gut symptoms
Dealing with persistent fatigue that doesn’t match your blood work

…it may be time to explore whether iron imbalance, inflammation, or the cellular danger response is playing a role.

You don’t have to figure this out alone. Iron homeostasis is nuanced. If you would like some support please get in touch and book a free clarity call with me.

References

Malesza, I. J., et al. (2022). The dark side of iron. Nutrients, 14(17), 36079734. https://doi.org/10.3390/nu14173478
Kortman, G. A., Raffatellu, M., Swinkels, D. W., & Tjalsma, H. (2014). Nutritional iron turned inside out: intestinal stress from a gut microbial perspective. FEMS microbiology reviews, 38(6), 1202–1234. https://doi.org/10.1111/1574-6976.12086
Baryshnikova N, Uspenskiy Y, Novikova V. Microbiota and iron metabolism. Explor Dig Dis. 2025;4:100585. https://doi.org/10.37349/edd.2025.100585
Loveikyte, R., et al. (2023). The effect of iron therapy on oxidative stress and intestinal microbiota: a review. Redox Biology. https://www.sciencedirect.com/science/article/pii/S2213231723003518
Kania, B., et al. (2023). The prevention of inflammation and the maintenance of gut-liver-brain axis: the role of hepcidin. Journal of Alzheimer’s Disease, 90(s1), S219-S230. https://doi.org/10.3233/JAD-220224