If you have been waking up tired for weeks, brushing more hair off your shoulders than usual, or finding it harder to think straight (and your last blood test came back “normal”), you are not imagining it. A basic NHS panel often misses the most likely cause: low ferritin.

Ferritin is the best single marker for whether your iron stores are truly low. It drops long before the usual signs of anaemia appear on a standard blood test. That means many people feel tired and foggy, and shed more hair than they should, for months, even though their results look fine on paper.

This article explains what low ferritin actually feels like, why it so often goes unnoticed, who is most at risk, and what to do about it. At WMG Health, our private blood testing service on Harley Street, London, same-day appointments and four-hour clinical reviews are standard.

What ferritin actually is

Ferritin is the protein your body uses to store iron. Think of it as the warehouse, not the delivery truck. Standard full blood counts measure haemoglobin (the truck delivering the iron), but they do not always show whether the warehouse is running low. By the time anaemia shows up on a full blood count (FBC), you have often had depleted iron stores for months, or even years.

That gap is where most people get stuck. Their bloodwork looks normal, but they feel flat, foggy, get out of breath more easily, and lose more hair than they should. It is a frustrating place to be, and it is why a ferritin test is one of the most useful tests in private blood testing.

What low ferritin actually feels like

Low ferritin tends to cluster a recognisable group of symptoms together rather than presenting with a single dramatic sign. The textbook picture includes:

  • Persistent tiredness that does not resolve with rest. Many patients describe sleeping eight hours and still waking up exhausted.
  • Diffuse hair shedding across the whole scalp rather than in patches. You may notice more hair on the brush or in the shower, or a widening parting.
  • Brittle nails, vertical ridges, or nails that bend and split unusually easily.
  • Getting out of breath from mild activity. Climbing stairs or walking quickly leaves you puffing when it did not before.
  • Restless legs at night, particularly when you are tired.
  • Brain fog and reduced concentration. Tasks that used to take an hour now take two.
  • Pale skin, or (more reliably) pale inner eyelids when you gently pull the lower lid down.
  • Cold hands and feet even in normal temperatures.

Less commonly, patients also report:

  • Pica: cravings for ice, clay, or other non-food items. This is a classic textbook sign of iron deficiency.
  • A sore tongue or mouth ulcers.
  • Unexplained itching of the skin.
  • Drier, duller hair in addition to the shedding.

You do not need all of these. Several together can point to low ferritin, and noticing a consistent pattern is the most important takeaway.

Who is most at risk

Low ferritin is statistically more common in:

  • Menstruating women, particularly those with heavier periods. This is the most common cause of low ferritin in adults under 50.
  • People on plant-based diets without supplementation. Plant iron (non-haem iron) is significantly less bioavailable than animal iron.
  • People who do a lot of endurance exercise. Running causes small, steady red blood cell turnover that lowers iron stores over time.
  • People recovering from pregnancy. Pregnancy and breastfeeding both draw significant iron from maternal stores.
  • Anyone with coeliac disease or other malabsorption conditions, where iron is not absorbed properly even when dietary intake is high.
  • Frequent blood donors. Each donation removes roughly 200 to 250 mg of iron.
  • People taking long-term acid-reducing medicines such as omeprazole or lansoprazole, which lower stomach acid and reduce iron absorption.

Stress and busy lives do not directly cause low ferritin, but they can mask the symptoms: tiredness gets blamed on burnout instead of a fixable nutritional problem. We see this a lot in busy professionals across London who put up with months of fatigue before getting tested.

Why a basic blood count is not enough

A normal full blood count does not mean your iron stores are adequate. Iron deficiency can exist without anaemia.

A standard NHS blood test (FBC) checks haemoglobin (the protein that carries oxygen), the red blood cell count, and a few related values. If your haemoglobin is above the cut-off (around 120 g/L for women and 130 g/L for men), you are not classed as anaemic, so many appointments stop there.

However, you can have non-anaemic iron deficiency for years before haemoglobin drops. Ferritin is the first marker to fall, sometimes by 60 to 80%, before anaemia ever appears. People with ferritin levels of 15 or 20 µg/L frequently feel unwell but are told their bloodwork is fine.

What “normal” really means for ferritin

UK lab reference ranges vary, but most flag the broad range of 30 to 400 µg/L as normal for adult women, with a slightly higher floor for men.

The problem is that a result of 35 µg/L, while technically inside the range, is functionally low for someone with hair shedding or unexplained fatigue. NICE guidance acknowledges that ferritin levels below 30 µg/L are diagnostic of iron deficiency, and many specialists treat levels up to 50 to 70 µg/L when symptoms are present, particularly in the context of telogen effluvium (the medical term for diffuse hair shedding).

This is why blood test results need to be read in context, not just as “normal” or “abnormal”. Every result in our Hair Loss Essentials panel is reviewed by a GMC-registered doctor who considers your numbers and your symptoms together.

What a complete ferritin diagnostic looks like

If you are investigating low ferritin properly, a single test is rarely enough. The complete picture includes:

  • Ferritin itself, the headline marker.
  • Full blood count (FBC) to confirm whether anaemia is also present.
  • Serum iron, total iron binding capacity (TIBC), and transferrin saturation to distinguish true iron deficiency from the anaemia of chronic disease.
  • Vitamin D, which commonly co-occurs with fatigue and hair shedding.
  • Vitamin B12, for the same reason.
  • Thyroid function (TSH), since hypothyroidism produces overlapping symptoms and is another leading reversible cause of hair loss.

A common first reflex is to walk into a pharmacy and grab an iron supplement. Do not do this. Iron is one of the few minerals the body has no efficient way to excrete in excess. Supplementing when you do not need it can cause short-term gut irritation and, over years, contribute to iron overload. The right approach is to confirm the deficiency, identify the underlying cause, and match the dose to the gap.

Once a diagnosis is confirmed, treatment usually involves:

  • Prescription-strength iron (such as ferrous sulfate or ferrous fumarate), often taken every other day for better absorption and fewer gut side effects.
  • Dietary support: vitamin C alongside iron-rich meals, and avoiding tea or coffee at mealtimes.
  • Investigating the underlying cause where it is not obvious, such as heavy menstrual loss or a gut absorption issue.
  • A repeat blood test at three months to confirm your levels are responding.

What changes when you get treated

When the deficiency is real and addressed correctly, patients usually notice:

  • Improved energy within four to six weeks.
  • Reduced hair shedding within eight to twelve weeks. Hair grows on a longer cycle, so the visible improvement lags but does come.
  • Restored exercise capacity and clearer concentration over a similar timeframe.

Ferritin responds more slowly than haemoglobin, which is why a repeat test around three months after starting treatment is standard, both to confirm the trend and to check whether the dose needs adjusting.

Getting tested at WMG Health

If you have had any of these symptoms for more than a few weeks (particularly hair shedding, persistent fatigue, or breathlessness on mild exertion), bloodwork is a sensible first step. It is also worth checking if you menstruate heavily, follow a vegetarian or vegan diet, train intensively, or have recently been pregnant.

You can book a same-day appointment for the Hair Loss Essentials panel at our Harley Street clinic. Results within four hours, reviewed by a GMC-registered doctor, with no GP referral required.

Sources

  • NICE Clinical Knowledge Summary: Anaemia – iron deficiency. cks.nice.org.uk
  • British Society for Haematology: UK guidelines on the management of iron deficiency in adults. b-s-h.org.uk
  • NHS: Iron deficiency anaemia overview. nhs.uk
  • Pasricha SR et al. Iron deficiency. The Lancet, 2021.

This article is for general information only and does not constitute clinical advice. If you have concerns about your symptoms, book an appointment or speak to your GP.