There is nothing more frustrating than feeling exhausted all the time, finally getting labs done, and seeing that your ferritin is low.
So you do everything you are told to do.
So you do everything you are told to do.
You take iron supplements. You eat more red meat. You add vitamin C. Maybe you even try an iron infusion.
But months later, your labs come back, and your ferritin barely moved.
At the same time, you might also be dealing with bloating after meals, constipation, or being told you have IBS or SIBO. At first, these issues seem unrelated. One looks like a blood lab issue, and the other looks like a gut problem.
But once you start connecting the dots, a pattern begins to appear. Many people struggling with iron deficiency are also dealing with underlying digestive dysfunction. When gut health is not working properly, the body often has a much harder time absorbing and using iron.
Understanding the connection between iron deficiency and gut health can completely change how you approach stubborn ferritin levels.
Why Iron Deficiency and Gut Health Are More Connected Than You Think
One of the biggest misconceptions about iron deficiency is that it is only about how much iron you consume.
In reality, iron status depends heavily on how well your digestive system is functioning.
Iron absorption primarily happens in the first portion of the small intestine, right after food leaves the stomach. Interestingly, this is also the area where small intestinal bacterial overgrowth, or SIBO, tends to develop.
This is where things start to get interesting. When bacteria accumulate in this region, they can interfere with the normal process of nutrient absorption.
I often explain this to clients using a simple analogy.
Imagine you keep ordering packages online, but they never arrive at your house. The company sends a replacement package, and that one does not arrive either. They send another and another, and still nothing shows up.
Eventually, you stop asking for more packages and start asking a different question.
What is happening with the delivery system?
This is often what happens with stubborn iron deficiency. The issue is not always how much iron you are taking in. The issue may be whether the system responsible for absorbing it is functioning well.
When the digestive system is struggling, iron may never make it to where it needs to go.
How Gut Bacteria Can Compete With Your Body for Iron
If bacteria are overgrowing in the small intestine, they can begin competing with the body for nutrients.
Certain microbes bind tightly to iron and use it for their own metabolic processes. In other words, bacteria may grab the iron before the body has a chance to absorb it.
This can create a frustrating situation where someone is doing everything right but still not seeing improvement in their labs.
For example, someone might be:
- Eating iron-rich foods
- Taking iron supplements consistently
- Adding vitamin C to improve absorption
Yet their ferritin barely moves.
This competition for nutrients is one reason digestive health plays such an important role in nutrient status. When the small intestine becomes crowded with bacteria, the body may simply not get first access to the nutrients it needs.
It helps explain why people can follow all the typical recommendations and still feel like nothing is changing.
When the Gut Lining Struggles, Nutrient Absorption Suffers
The small intestine is designed to absorb nutrients incredibly efficiently.
Inside the intestine are tiny finger-like structures called villi that dramatically increase the surface area available for absorption. If that surface area were stretched out, it would be roughly the size of a tennis court.
This large surface area allows the body to capture nutrients from food as efficiently as possible.
But when bacterial overgrowth is present, this environment can become irritated and inflamed.
Over time, this inflammation can affect the structure of the intestinal lining. Those finger-like projections that help absorb nutrients can become shorter or less effective, which reduces the total surface area available for absorption.
When this happens, the body becomes less efficient at pulling nutrients from food.
Iron is often one of the first nutrients affected because it relies heavily on the health of the small intestine for proper absorption. But it is rarely the only nutrient impacted. People with chronic digestive issues may also struggle with absorbing nutrients like vitamin B12, fat-soluble vitamins, and other minerals.
When the gut lining is inflamed, the body simply cannot absorb nutrients as efficiently as it should.
Inflammation Can Block Iron From Circulating
Even when iron is present in the body, another system controls whether that iron is actually allowed to circulate.
This system is regulated by a hormone called hepcidin.
Hepcidin acts like a traffic controller for iron. It determines how much iron is absorbed from the intestine and how much iron is released into circulation.
When inflammation increases, hepcidin levels rise. When hepcidin rises, the body slows down iron absorption and traps iron inside storage cells.
This is actually part of the body’s defense system. Many microbes rely on iron to survive. When the body detects inflammation or infection, it temporarily limits iron availability so bacteria cannot access it.
The problem occurs when inflammation becomes chronic.
In that situation, iron may technically be present in the body, but the body is not allowing it to move where it needs to go. This pattern is sometimes referred to as functional iron deficiency.
People may feel extremely fatigued and have symptoms of low iron, yet iron supplementation still does not seem to move the needle.
The Often Overlooked Root Cause: Low Stomach Acid
Another piece of the puzzle often shows up much earlier in the process than most people realize. Before SIBO develops or ferritin becomes stubbornly low, digestion may already be struggling due to low stomach acid.
Stomach acid is one of the first steps in proper digestion, and when it is not functioning well, it can create a ripple effect throughout the entire gut.
Here are a few important ways low stomach acid can begin disrupting iron absorption and gut health:
Iron becomes harder to absorb
Stomach acid helps convert iron from food into a form that the body can absorb in the small intestine. When stomach acid is low, this conversion does not happen efficiently. Even if someone is eating iron-rich foods or taking supplements, the body may not be able to use that iron effectively.
Bacteria can survive and move deeper into the gut
One of the stomach’s jobs is to act as a barrier against unwanted microbes that enter through food. When stomach acid levels are strong, many of these bacteria are neutralized before they reach the small intestine. When stomach acid is low, more bacteria can survive and migrate further into the digestive tract.
The risk of bacterial overgrowth increases
Once bacteria begin accumulating in the small intestine, the environment becomes more vulnerable to bacterial overgrowth. Over time, this can disrupt digestion even further and interfere with nutrient absorption. This is one of the reasons digestive symptoms and nutrient deficiencies often appear together.
By the time someone is dealing with both digestive symptoms and stubborn iron deficiency, this chain reaction has often been developing for quite some time. Supporting digestion at the top of the system can be an important step toward helping the body absorb and use nutrients more effectively.
Why Iron Deficiency and Gut Health Should Be Addressed Together
If you have struggled with low ferritin that refuses to improve, or digestive issues like bloating, constipation, or recurring SIBO, it may be worth asking a different question.
Instead of focusing only on how to increase iron intake, the more helpful question may be how well your digestive system is functioning.
Because when digestion, motility, and microbiome health begin to improve, the body often becomes much better at absorbing and using nutrients.
That is when ferritin levels often start moving in the right direction.
If this topic resonates with you and you are someone who has struggled with SIBO, bloating, constipation, or iron levels that refuse to budge despite doing all the right things, the next step is to start looking at the full digestive picture rather than chasing individual symptoms.
If you want to go deeper on this topic, you can listen to the full podcast episode where I walk through the physiology behind iron deficiency and gut health, and why ferritin often will not improve until digestion is addressed.
And if you are dealing with ongoing bloating, constipation, or recurring SIBO and want help identifying the root cause of your symptoms, you can also start by taking my Gut Health Quiz, which helps you identify which digestive systems may need the most support.
For those ready for deeper support, the gutTogether program walks you through the exact process we use with clients to restore digestion, support motility, rebalance the microbiome, and improve nutrient absorption so that your gut and your labs finally start moving in the right direction.
Because when the system starts working again, everything else becomes much easier to fix.
