Not to be considered personalised medical advice. For information and guidance only.
I wanted to do a deep dive into iron: why you need it checking and what to do if your levels are low.
This is one of the most common problems I see in my female patients and can sometimes be more complicated than it first seems.
So let's get the terminology right first. These terms are often used interchangeably, so it's important to be clear.
What is iron?
Iron is the mineral your body uses to make haemoglobin, which allows red blood cells to carry oxygen to all the areas of the body that need it.
Ferritin is the protein that stores iron, creating your body's iron reserve.
So you can think of iron as the money in your wallet and ferritin as your bank account, releasing more iron into your bloodstream (your wallet) when you need it.
Ferritin can become low even when your blood iron levels are relatively normal. There's still money in your wallet, but the savings are emptying rapidly!
This is why we check ferritin rather than iron levels alone. It's a better indicator of the overall picture.
There are some rare exceptions where ferritin becomes falsely elevated, which we'll discuss in more detail on our upcoming podcast, Rooted Conversations.
Haemoglobin is the iron-containing protein in your red blood cells that binds oxygen, supplying the body with the oxygen it needs.
These facts are all important for you to be able to interpret your results.
So you can have a normal haemoglobin but low ferritin. This means you are not yet anaemic, but your stores are low, so it's likely you might become anaemic if nothing changes. Or both your haemoglobin and ferritin are low, which is what's termed iron deficiency anaemia.
It is generally thought that hair needs a ferritin of at least 70 µg/L to grow effectively. The "normal" range in the UK is roughly 30 to 322, so even when your results are normal, they might be low for hair growth.
Why does it matter?
When iron stores fall significantly, the body may eventually struggle to produce enough healthy red blood cells, leading to iron deficiency anaemia. It is suspected that hair is not prioritised by the body in these circumstances, with the nutrients supply diverted to other areas. It is well documented that in some types of hair loss, such as telogen effluvium low iron is a causative factor.
How does it feel to have low iron?
It can mean you are not dramatically unwell, just more tired than usual. You may feel colder, more breathless, less able to concentrate, or simply as though everyday life is taking more effort.
Your hair may be shedding or not feeling like it used to. It's very easy to oversimplify the link between iron and hair loss.
Then you have some blood tests and are told:
"Your iron is low."
It sounds simple. Take some iron and the problem is solved.
But iron deficiency is often more complicated than that.
If someone is genuinely iron deficient, the important next question is:
Why is the iron low?
Low iron is not the final diagnosis.
It is a clue.
We then need to work out where the iron has gone.
This is why it is important to have someone who understands your numbers in context, and who can examine you and look at the whole picture.
Heavy periods
In women who menstruate, one of the most common causes is blood loss through periods.
It is not always enough to ask:
"Are your periods heavy?"
People have very different ideas about what is normal. If heavy menstrual bleeding is driving iron deficiency, simply replacing iron without addressing the blood loss may mean the problem keeps returning.
Pregnancy
Pregnancy increases the body's iron requirements considerably.
People who have had several pregnancies, pregnancies close together, or who began pregnancy with relatively low iron stores may be more vulnerable to iron deficiency.
Diet
Diet can contribute, particularly if someone eats very little iron-containing food.
However, iron deficiency should not automatically be blamed on diet. There may be other reasons why iron is being lost or not properly absorbed.
Particular exclusion diets and weight loss medications can have an impact, so it's always important to highlight these to your doctor.
Poor iron absorption
Iron is absorbed through the gastrointestinal tract.
Conditions affecting the gut can therefore lead to iron deficiency, even when someone appears to eat a perfectly reasonable diet.
One important example is coeliac disease.
Coeliac disease can interfere with iron absorption and, importantly, not everyone with coeliac disease experiences obvious digestive symptoms.
This is why coeliac disease is often considered when investigating unexplained iron deficiency anaemia, and it's often one of the first things I explore when looking into why iron is low.
Excessive iron loss
Blood can be lost through the gastrointestinal or urological tract. There are simple tests you can do to rule this out. Some medications can make this more likely.
What can you do about it?
There is no single magic ferritin level at which everyone's hair suddenly begins or stops growing.
Hair shedding in particular has many possible causes, so blood tests always need to be interpreted alongside your symptoms, medical history, examination and the pattern of hair loss.
"I've taken iron for months, but my levels barely move"
This is something I hear surprisingly often.
If iron levels remain low despite treatment, we need to ask whether the iron is actually being absorbed.
There are several reasons why this may not happen.
Tips and tricks to improve iron absorption
Before we look at which iron tablet you're taking, it's worth asking how and when you're taking it. A few small changes to your routine can make a real difference.
Tea and coffee
If you take your iron tablet and follow it within an hour with a cup of tea or coffee, you may reduce how much iron your body absorbs. Both contain compounds that interfere with absorption. Leave a decent gap between the two.
Calcium
Milk, yoghurt, cheese and calcium supplements can also affect absorption. Best to keep them away from your iron too.
Acid-reducing medicines
Proton pump inhibitors, or PPIs, include omeprazole, lansoprazole and esomeprazole. They reduce the amount of acid your stomach makes.
They're extremely useful medicines. But stomach acid also helps make iron available for absorption, so for some people, particularly with long-term use, they can make it harder to absorb iron.
This doesn't mean you should stop a prescribed PPI. It does mean that if your iron stays low despite treatment, your medication list deserves a proper review.
Iron and levothyroxine
If you take levothyroxine for an underactive thyroid, this one's for you. Iron can reduce how well levothyroxine is absorbed, so taking them together isn't a good idea. Levothyroxine is sensitive to timing, so talk to your pharmacist about the best routine for you.
Supplements: what should I be taking?
Most people are prescribed a standard once-daily tablet. Common options include ferrous sulphate and ferrous fumarate. A ferrous sulphate 200mg tablet, for example, contains around 65mg of elemental iron.
Iron tablets aren't always easy to tolerate. Side effects can include:
nausea
constipation
abdominal discomfort
diarrhoea
darker stools
If this happens, don't assume treatment has failed. There may be a different preparation or dosing schedule that suits you better, and some people do well taking iron on alternate days. The right approach should be tailored to you.
Which foods contain iron?
Food can make a useful contribution. There are two types of dietary iron.
Haem iron, found in meat, tends to be absorbed more easily.
Non-haem iron, found in plant foods, is still of value, although how much you absorb depends more on what you eat and drink with it.
Some approximate examples:
70g beef: around 2mg
100g cooked red lentils: around 2.4mg
200g baked beans: around 2.8mg
100g cooked soya beans: around 3mg
80g kale: around 1.6mg
30g cashew nuts: around 1.9mg
1 tablespoon pumpkin seeds: around 1mg
Fortified breakfast cereal: often 2 to 4mg per serving, depending on the brand
A plant-based diet can absolutely give you meaningful amounts of iron.
Help your body absorb it
Vitamin C helps your body absorb non-haem iron. Easy pairings include:
lentils with tomatoes
beans with peppers
Hummous & red pepper
fortified cereal with berries or kiwi
chickpeas with tomatoes and lemon
No need to overthink it. A varied diet with pulses, beans, nuts, seeds, fortified foods, green veg and, if you eat it, meat will all help. Just remember that a strong cup of tea straight after an iron-rich meal may cancel out some of the benefit.
Your treatment should be checked
Iron treatment shouldn't mean being handed a prescription and forgotten about. Repeat blood tests matter.
If the diagnosis is right and the iron is being absorbed, your results should start to improve. If they don't, it's worth asking:
Is there still ongoing blood loss?
Are the tablets being tolerated and taken?
Is another medicine interfering?
Could coeliac disease or another gut condition be involved?
Is the diagnosis correct?
Is oral iron enough?
For some people, intravenous iron may be considered, particularly if tablets aren't tolerated, aren't working, or absorption is a real problem.
A normal haemoglobin doesn't mean you're finished
Once your haemoglobin is back in range, it's tempting to stop. But your body may still need time to rebuild its stores, which is why iron is often continued for a while afterwards.
What does this mean for your hair?
Hair shedding is often what prompts women ( Or men) to look into their general health. But not every case of hair loss is caused by low iron.
Hair loss can be linked to genetics, thyroid disease, illness, rapid weight loss, nutritional deficiencies, hormonal changes, medications, stress on the body and scalp conditions.
So it's important not to jump to one explanation. Hair loss deserves a proper assessment. And if low iron turns up along the way, it deserves proper treatment and proper investigation.
If you remember one thing
Low iron deserves a "why".
If your hair is shedding, you're exhausted and your bloods confirm iron deficiency, replacing the iron matters. Understanding why you became deficient matters just as much.
For one woman, it's heavy periods. For another, coeliac disease. For someone else, a medication quietly blocking absorption. And in men or post-menopausal women with unexplained iron deficiency anaemia, further investigation is particularly important.
Good medicine isn't just about turning an abnormal result into a normal one. It's about understanding why it became abnormal in the first place.
Sometimes your hair is the first sign that tells us to look a little deeper.