Nutrition and iron status
Anemia, low ferritin, and recurring iron deficiency are not always just about how much iron you eat — absorption is just as important.
Many people eat what they think is enough iron and still feel tired, become short of breath easily, or are told by their GP that their ferritin is on the low side. Here, we explain why iron intake and iron absorption are not the same thing, and what actually determines how much iron your body can access.
You eat meat, eggs, and leafy green vegetables.
You try to eat a varied diet. Maybe you even take an iron supplement. And still, you feel tired in a way that sleep doesn't fix. You get short of breath climbing stairs you used to run up. Your concentration fails in the middle of the day.
And when you finally have blood tests, your GP might say: "Your ferritin is low."
"But I eat iron-rich foods. How can I still be low in iron?"
It's one of the most common questions we get in the clinic. And the answer is rarely just about how much iron is on your plate. It's about how much of that iron your body can actually absorb.
Why iron matters for your energy
Iron is part of hemoglobin — the protein in red blood cells that carries oxygen from your lungs to every cell in your body. Iron is also part of many enzymes involved in cellular energy production.
According to the Norwegian Directorate of Health's reference values, iron is a nutrient that contributes to normal oxygen transport in the body, normal energy metabolism, and normal cognitive function. When iron stores fall, these are precisely the functions that are affected first — causing fatigue, reduced concentration, and lower physical capacity.
Ferritin — your body's iron stores
Hemoglobin tells us a lot about the body's ability to transport oxygen. But hemoglobin is not the same as the body's iron stores.
That's where ferritin comes in. Ferritin is used as a marker of the body's stored iron — which means your hemoglobin can be within the reference range even when your iron stores are low.
That's why in the clinic, we rarely look at just one number on its own. We want to understand the relationship between ferritin, hemoglobin, other iron-status markers, symptoms, menstruation/blood loss, diet, and digestion. Ferritin can also be affected by inflammation in the body, so a single ferritin result doesn't always tell the whole story — it should be interpreted by a doctor or Clinical Nutritionist alongside the rest of the picture.
Four main reasons why iron stores may be low
Not enough iron coming in
You don't get enough iron from your diet.
Your body needs more
For example, during growth or pregnancy.
You lose more iron than your body can replace
Heavy periods or other bleeding can gradually deplete iron stores.
Your body absorbs too little of the iron you get
You can eat iron-rich foods and still absorb too little.
That's why low ferritin doesn't automatically mean the solution is to eat or take more iron. First, we need to understand why your stores are low.
Your iron needs aren't the same as your neighbor's
How much iron your body needs depends on factors including sex, age, menstruation, pregnancy, and growth. That's why it makes little sense to talk about "enough iron" without knowing who we're talking about.
Reference values
Daily iron requirements by life stage
Based on the Norwegian Directorate of Health's reference values / Nordic Nutrition Recommendations (NNR2023).
| Group | Reference intake | Why the requirement is what it is | Example food sources |
|---|---|---|---|
| Women aged 15–50 | 15 mg | Regular iron loss through menstruation | 150 g ground beef + 150 g lentils + 50 g liver pâté (≈14 mg) |
| Women over 50 | 8 mg | Lower losses after menopause | 100 g ground beef + 100 g chickpeas + 1 egg (≈7 mg) |
| Pregnant women | 26 mg | Increased blood volume and the fetus's needs | 150 g ground beef + 150 g lentils + 100 g black pudding (≈20 mg — often difficult to meet fully through food alone; iron supplements are therefore routinely recommended during pregnancy, in consultation with a midwife/doctor) |
| Breastfeeding women | 15 mg | Increased nutritional needs during breastfeeding | 150 g ground beef + 150 g lentils + 50 g liver pâté (≈14 mg) |
| Men aged 18+ | 9 mg | No menstruation-related losses | 100 g ground beef + 100 g chickpeas + 1 egg (≈7 mg) |
| Girls aged 11–14 | 13 mg | Growth spurt + onset of menstruation | 100 g ground beef + 100 g lentils + 100 g chickpeas + 30 g liver pâté (≈12 mg) |
| Boys aged 11–14 | 11 mg | Growth spurt | 100 g ground beef + 100 g lentils + 30 g liver pâté + 1 egg (≈10 mg) |
| Children aged 1–10 | 7–9 mg | Growth and development | 75 g ground beef in sauce + a little lentils/chickpeas + 20 g liver pâté + 1 egg (≈7 mg) |
The food-source examples are based on Matvaretabellen.no and show realistic combinations — not a complete meal plan. We have deliberately limited these combinations to meat, offal, legumes, and eggs, leaving out whole grains because the phytic acid in whole grains can reduce iron absorption (see section below). The quantities show the iron content in the food, not how much is actually absorbed. The reference values are general, and individual needs should be assessed by a doctor or Clinical Nutritionist, especially if iron deficiency is suspected in a child.
Two types of iron — and why the body handles them differently
Not all iron is the same to the body. There are two main types, and they are absorbed in very different ways.
This is one of the main reasons vegetarians and vegans are often advised to have a higher iron intake than meat eaters — not because plant sources contain less iron in themselves, but because the body normally absorbs less of it.
Why you can eat enough iron and still have low stores
Iron absorption in the gut is strongly affected by what you eat alongside the iron. That's why two people can eat roughly the same amount of iron and end up with very different iron status.
These increase iron absorption:
- Vitamin C in the same meal (bell peppers, citrus fruit, broccoli)
- The "meat factor" — meat, fish, or poultry can improve the absorption of non-heme iron in the same meal
- Spreading iron-rich meals throughout the day
These reduce iron absorption when consumed at the same time:
- Tannins in coffee and tea consumed with a meal
- Calcium from dairy products or supplements taken at the same time
- Phytic acid in whole grains, legumes, and nuts
- Oxalic acid in foods including spinach
We're not saying that coffee, milk, whole grains, or spinach are unhealthy — they are valuable parts of a varied diet, and several of them (such as whole grains and spinach) are themselves good sources of iron. The point is timing and combination: having iron-rich meals or iron supplements a few hours apart from coffee, tea, or calcium-rich products, and preferably alongside vitamin C, can help your body access the iron more effectively. If you suspect iron deficiency, ferritin and other iron-status markers should always be assessed through blood tests by a doctor.
What you can do today
- Eat iron-rich foods regularly.
- Especially pair plant-based sources of iron with vitamin C.
- Avoid having coffee and tea with your most iron-rich meals.
- Remember that the iron content in food isn't the same as the amount of iron your body actually absorbs.
Who should pay extra attention to their iron status?
Women of reproductive age
Menstruation involves regular iron loss, and this is the main reason the reference intake for women aged 15–50 is almost twice as high as it is for men. Heavy menstrual bleeding can increase requirements even further.
Athletes and physically active people
People who are very physically active can lose more iron than others — through sweat, minor bleeding in the gastrointestinal tract during endurance training, and increased breakdown of red blood cells from repeated impact on the feet ("foot-strike hemolysis" in runners). At the same time, exercise increases the body's overall need to transport oxygen.
Vegetarians and vegans
A diet without meat, fish, and poultry doesn't provide heme iron, so it relies on the less efficiently absorbed non-heme iron — from sources such as lentils, beans, chickpeas, mushrooms, spinach, and other dark leafy greens. Pairing these foods with vitamin C and being mindful of timing around coffee, tea, and calcium is especially important.
Iron needs are also high during periods of rapid growth, such as in children and adolescents (see the table above). For children, diet, supplements, and any suspected iron deficiency should always be assessed with a GP or public health nurse.
Iron and thyroid function — an important connection
Iron also plays a role in thyroid function. The enzyme thyroid peroxidase (TPO), which the thyroid gland needs to produce the hormones T3 and T4, requires iron to function normally.
This is one reason why symptoms of iron deficiency and symptoms of an underactive thyroid (hypothyroidism) can often resemble one another — both can cause fatigue, feeling cold, difficulty concentrating, and low energy. In the clinic, we therefore often consider iron status and thyroid markers such as TSH, free T4, and, where relevant, TPO antibodies together rather than assessing them separately.
If you have persistent symptoms of an underactive thyroid, you should always have them investigated with blood tests by a doctor. Iron status is only one of several pieces of the puzzle.
Your digestion determines how much iron is actually absorbed
When should we take a closer look at digestion?
Digestion isn't the cause of every case of iron deficiency. But it's particularly relevant when low iron stores occur alongside digestive symptoms or other signs that nutrient absorption may be affected.
This is especially true if you also have bloating, reflux, discomfort after meals, long-term diarrhea or constipation, a diagnosed bowel condition, or low levels of several nutrients.
Iron is absorbed mainly in the first part of the small intestine. Before iron can be absorbed, it must be available in a form that intestinal cells can handle.
Stomach acid plays a particular role in the absorption of non-heme iron by helping release the iron from food and keep it available for further absorption. The iron then has to pass through the cells in the intestinal lining before it can be transported through the body.
That's why what you eat, how your meal is put together, and how your gastrointestinal system functions can all affect how much of the iron in food is actually available to your body.
We're not saying that Digestive Support treats or prevents iron deficiency. It does not, and iron deficiency should always be investigated and followed up by a doctor when needed, ideally with blood tests such as ferritin and transferrin saturation. The point is different: good digestive function is a prerequisite for the iron in food — and in any supplements — to be available to the body in the first place.
That's why we often see the following in practice: some people eat iron-rich foods and even take an iron supplement, yet their ferritin still doesn't rise as expected. In that case, the question isn't necessarily "Do I need more iron?" but "Can my body absorb the iron I'm already getting?"
If you still feel low in iron despite eating iron-rich foods and taking supplements, it may be worth taking a closer look at your digestion, not just the amount of iron.
Why we don't start everyone on high doses of iron
When you feel low in iron, it's tempting to think the solution is an iron supplement with the highest dose possible. In the clinic, this is rarely our first recommendation, and there's a reason for that.
When iron supplements improve iron status — but upset your stomach
With confirmed iron deficiency, iron supplements can be both necessary and important. The goal isn't to avoid iron treatment when your body genuinely needs it.
But oral iron supplements can cause constipation, nausea, stomach pain, diarrhea, and dark stools for some people. If this happens, it doesn't necessarily mean you should stop treatment. However, the dose, formulation, and how you take the iron may need to be reviewed with a doctor or other qualified healthcare professional.
Your body actually has its own system for regulating how much iron it lets in.
A hormone called hepcidin acts a little like a gatekeeper for iron absorption. After a larger dose of iron, hepcidin levels can rise for a while. This can cause the body to absorb a smaller proportion of the next dose.
Studies of oral iron salts have shown that this effect can last into the following day. This is one reason why more iron and more frequent dosing don't automatically mean that more iron will be absorbed.
That's why the dose and dosing schedule should be tailored to the confirmed deficiency and the individual.
But what if ferritin falls again?
This is the question I think we should ask more often.
If your ferritin rises while you're taking iron supplements but falls again after you stop treatment, the treatment may have replenished your stores — but we still need to understand why they're being depleted again.
Then the only question isn't:
"Which iron supplement should I take now?"
We should also ask:
Am I getting enough? Am I losing too much? Have my needs increased? Or is something affecting absorption?
When iron stores are repeatedly or persistently low, the cause should therefore be assessed, rather than simply treating the ferritin level again.
That's why we generally start by understanding why iron stores are low — diet, absorption, loss, or a combination — rather than addressing every case with the same high dose.
Dosing iron supplements for confirmed iron deficiency should always be discussed with a doctor, who can also assess blood test results and any underlying cause. This is especially important for conditions such as hemochromatosis, where increased iron intake can be directly harmful. This article provides general information and does not replace an individual medical assessment.
How to support better iron absorption
Pair iron-rich meals with vitamin C, and have coffee, tea, and calcium-rich products at other times of the day if possible. And if you already eat well and perhaps take iron supplements, but still feel low in iron, it may also be worth looking at how your digestion is functioning — since digestion ultimately determines how much of the iron is actually available for your body to use.
When should you investigate further?
Diet and digestion are often part of the picture — but certain signs should always be followed up with blood tests from a doctor, regardless of what you eat:
- Persistent fatigue or reduced capacity that doesn't improve with rest or dietary changes
- Marked paleness, palpitations, or shortness of breath during ordinary activity
- Heavy or prolonged menstrual bleeding
- Known digestive problems, such as persistent bloating, changes in bowel habits, or suspected celiac disease or another bowel condition
- Pregnancy, regardless of symptoms
- Family history of iron-deficiency anemia or hemochromatosis
This list is not exhaustive and does not replace a medical assessment. Blood tests such as hemoglobin, ferritin, and, where relevant, transferrin saturation provide the clearest picture of iron status.
If digestive symptoms are part of your picture, it may also be relevant to work on digestive function — as one of several areas that affect how much iron your body can actually access.
Low ferritin — what should you do now?
You have symptoms but don't know whether you're low in iron
→ Don't guess based on symptoms alone. Start with relevant blood tests and a medical assessment.
You get little iron from your diet
→ First, work on including regular sources of iron and combining foods more effectively.
You have heavy periods or possible blood loss
→ Don't focus only on food. The cause of the iron loss should be assessed.
You have confirmed iron deficiency and have been advised to take an iron supplement
→ Treat the deficiency and follow up with blood tests as agreed.
Iron supplements cause constipation, nausea, or stomach pain
→ Don't simply increase the dose or push through the symptoms. Discuss the formulation, dose, and dosing schedule with a healthcare professional.
Your ferritin improves with iron but falls again
→ Now the question has to be why your iron stores are being depleted again.
You eat iron-rich foods but also have digestive symptoms or several nutrient deficiencies
→ In that case, it's relevant to investigate digestion and possible causes of reduced absorption in more detail.
The PureNordic principle: Find the function first
Iron deficiency is a finding. The next question is why it occurred.
For one person, it's mainly about not getting enough iron in their diet. For another, it's about heavy periods. For a third, it's about increased needs. And for some, we need to investigate whether digestion or a gastrointestinal condition is affecting absorption.
That's why we have two goals:
Correct a confirmed deficiency when necessary.
Understand why the deficiency occurred — especially when it comes back.
That's what we mean by Find the function first.
What people say after using Digestive Support
Here's what people report after using Digestive Support regularly over time. Individual results and needs vary.
"My digestion has improved significantly. I hardly get bloated anymore, and my stomach feels lighter after meals."
— Mats, Oslo
"Works well for my IBS."
— Runar, Kristiansand
"It worked really well for me; I'm on my second bottle. Recommended."
— Ifrah, Oslo
"After 2 months of PureNordic supplements, my health has improved significantly. Thank you."
— Sławomir, Poznań
What people commonly report: less bloating, greater regularity, and a sense that their digestion is "working with them" better. How much this affects the absorption of nutrients such as iron varies from person to person.
Has your ferritin been low several times?
Have you already changed your diet or taken iron supplements, but your iron stores keep falling again?
Then the next step may be to find out why.
During a consultation, we assess factors including diet, blood tests, menstruation/blood loss, digestion, other nutrient deficiencies, and which areas may need further investigation.
The goal isn't just to replenish your iron stores. The goal is to understand why the problem keeps coming back.
Book a consultation →Dietary supplements are not a substitute for a varied diet and a healthy lifestyle. If you have an illness, persistent or new symptoms, are pregnant, or take medication, consult a doctor or other qualified healthcare professional before using supplements. Individual needs vary. This article has been prepared for general information and does not replace individual medical advice.
