Quick answer: Yes, low iron can cause hair loss. The NHS lists hair loss as a symptom of iron deficiency anaemia, and iron deficiency is one of the temporary causes of hair loss it names. The most useful test is ferritin, which measures your iron stores, alongside a full blood count. Ask your GP for both. Don't start iron tablets without a test: if you're not low, extra iron won't help your hair and can cause side effects.
If I had to name the single most common thing I find behind "my hair has been shedding for months and I don't know why", it would be low iron. Especially in women. Especially in women with heavy periods, women who've had a baby in the last year or two, and anyone who eats little or no red meat.
It's also one of the easiest causes to check, which is why I'm slightly obsessed with it at Tess Hair and Scalp Clinic in Belfast. So here's the plain-English version: what iron has to do with hair, what ferritin means, what to ask your GP for, and what to do with the answer.
What iron has to do with your hair
Hair follicles are some of the fastest-dividing cells in your body. Growing hair takes a lot of energy and raw materials, and iron is central to both: it carries oxygen in your blood and is involved in making new cells.
When iron runs short, your body prioritises. It keeps iron for the things that keep you alive (your blood, your heart, your brain) and quietly rations it to things it considers optional. Hair is top of the optional list. Follicles slow down, more hairs slip into their resting phase, and a few months later you notice the shedding.
The NHS lists hair loss among the symptoms of iron deficiency anaemia ("you notice more hair coming out when brushing or washing it"), alongside the better-known ones: tiredness, shortness of breath, heart palpitations, paler skin and headaches. And on its hair loss page it names iron deficiency as one of the causes of temporary hair loss.
Ferritin: the test that actually matters for hair
Here's where a lot of people get told "your bloods are fine" and go home still shedding.
A standard blood test for anaemia looks at your haemoglobin (the red blood cells themselves). You can have perfectly normal haemoglobin and still have low ferritin. Ferritin is a protein that stores iron, and your ferritin level is the best everyday measure of how much iron you have in reserve.
Think of haemoglobin as the money in your purse and ferritin as the money in your savings account. You can have enough in your purse for today while your savings are nearly empty. Hair, annoyingly, seems to care about the savings account.
So when you ask your GP about hair loss, ask specifically for ferritin as well as a full blood count.
What's a "good" ferritin level for hair?
This is the honest bit. There isn't an agreed number.
A large 2019 review in the journal Dermatology and Therapy (Almohanna and colleagues) went through the research on vitamins, minerals and hair loss. On iron, it found that "the association of hair loss and low serum ferritin level has been debated for many years", that studies have defined iron deficiency anywhere from a ferritin of 15 up to 70, and that "there is no consensus on 'normal ferritin' levels". What most of the researchers did agree on was supplementing iron in people whose ferritin is low.
In practice, many trichologists and dermatologists are happier when ferritin is comfortably above the bottom of the laboratory's normal range rather than scraping along it, and some aim higher in people with active shedding. Your GP interprets your result in the context of everything else about you, which is the right way round. What I'd push back on is being told "normal" when the number is right at the bottom of the range and your hair is on the floor. That's worth a conversation.
Who's most likely to be low
Women with heavy periods. The NHS names heavy periods as one of the most common causes of iron deficiency.
Pregnancy and the year after. Growing a baby uses a lot of iron, and the NHS notes pregnancy deficiency is usually down to not enough iron in the diet.
Vegetarians and vegans. Plant iron is absorbed less well than iron from meat. It's perfectly possible to get enough, but it takes more attention.
Anyone with gut problems such as coeliac disease, or who has had bleeding in the stomach or bowel (the NHS flags this as a cause that needs looking into).
People on very restricted diets or who have lost a lot of weight quickly.
Regular blood donors and endurance athletes.
What to ask your GP
Keep it simple. Say: "I've had increased hair shedding for a few months and I'd like to rule out the common causes. Could I have a full blood count, ferritin, thyroid function and vitamin D?"
Those four cover the big, treatable, whole-body causes of shedding. Your GP may add others depending on your history. If your ferritin is low, the NHS says the GP will usually also want to understand why it's low, which matters, because treating the cause (heavy periods, a gut problem) stops it coming straight back.
Ask for the actual numbers, not just "normal". Write them down. If you then come to see me, bring them.
If your iron is low
The NHS advice is iron tablets, usually for about six months, with repeat blood tests to check the levels are recovering. A few practical points from the NHS page that make a real difference:
Taking the tablets with a glass of orange juice may help absorption (vitamin C helps iron get in).
Taking them with or after food can reduce side effects such as constipation, feeling sick or dark stools.
Keep taking them even if side effects are annoying; talk to your GP or pharmacist about options rather than just stopping.
Keep iron tablets well away from children. The NHS warns an overdose can be fatal in a young child.
And manage your expectations on timing. Hair works on a delay in both directions. It took months for low iron to show in your hair, and it'll take months after your levels recover for the hair to catch up. Three to six months before you see a real difference is typical.
Eating for better iron
The NHS suggests eating more:
dark green leafy vegetables (kale, spinach, watercress, spring greens)
iron-fortified cereals and bread
meat, especially red meat
dried fruit such as apricots, prunes and raisins
pulses: beans, peas and lentils
And eating or drinking less of the things that block iron absorption at mealtimes: tea, coffee, milk and dairy, and foods high in phytic acid such as wholegrain cereals. (You don't have to give them up. Just don't have your tea with your steak.)
A squeeze of lemon or a glass of orange juice with an iron-rich meal helps absorption. If you're vegan, the 2019 review mentioned above also notes the importance of vitamin C intake and suggests L-lysine supplementation can help iron status in some cases, which is worth raising with your GP or a dietitian.
Common mistakes
Buying iron tablets "just in case". If you're not low, they won't help your hair, and they can upset your stomach. Test first.
Taking a multivitamin and assuming it's enough. Most contain small amounts of iron that won't correct a real deficiency.
Stopping the tablets after a few weeks because the hair hasn't changed yet. The hair is the last thing to catch up.
Treating ferritin as the whole answer. Low iron often sits alongside another cause: a thyroid issue, pattern hair loss, or a scalp condition. Fix the iron and then look again.
Frequently asked questions
Does low iron cause hair loss?
Yes. The NHS lists hair loss as a symptom of iron deficiency anaemia and names iron deficiency as a cause of temporary hair loss.
What is ferritin?
Ferritin is a protein that stores iron. Your blood ferritin level is the best everyday measure of your iron reserves, which is why it's the test trichologists ask about.
What ferritin level causes hair loss?
There's no agreed number. Research has used cut-offs from 15 to 70. Many clinicians like to see ferritin well above the bottom of the normal range in someone with active shedding.
Will my hair grow back after treating low iron?
Usually, yes, but slowly. Expect three to six months after your levels recover before you notice a clear difference.
Can I take iron for hair loss without a blood test?
I wouldn't. Iron isn't harmless in excess, and if iron isn't your problem you'll have wasted months. A test is quick and your GP can arrange it.
Been shedding for months with no clear reason?
Book a hair and scalp analysis with Theresa at Tess Hair and Scalp Clinic, 77a Botanic Avenue, Belfast, or call 028 9096 4731. Bring your blood results if you have them. We'll look at your scalp, go through your history, and help you make sense of the numbers and the hair together. Our treatments and prices are here.
About the author: Theresa Anthony is the trichologist at Tess Hair and Scalp Clinic, 77a Botanic Avenue, Belfast BT7 1JL, where hair loss treatment and a full hair salon sit under one roof.
Sources: NHS: Iron deficiency anaemia · NHS: Hair loss · Almohanna et al. (2019), The Role of Vitamins and Minerals in Hair Loss: A Review, Dermatology and Therapy (link)
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