Low Ferritin, Normal Haemoglobin: Why You Feel Exhausted When Your GP Says Your Bloods Are “Normal” | OptiBlood UK

The hidden cause of fatigue your GP blood test may not flag

If you have been told your bloods are normal but you are still exhausted, losing hair or struggling to concentrate, you are not imagining it. Non-anaemic iron deficiency — depleted iron stores without full-blown anaemia — is common, and it is easy to miss.

A routine GP full blood count (FBC) looks at haemoglobin first. Haemoglobin carries oxygen, and when it falls you are anaemic. But haemoglobin can sit technically within range while your iron stores are already running low. Ferritin, the protein that stores iron, is often not requested, or is reported as normal while sitting at the very bottom of the range.

Haemoglobin is your current account; ferritin is your savings

Think of haemoglobin as the cash in your current account and ferritin as your savings. You can pay today’s bills while your savings account sits nearly empty. The account still functions — until it cannot.

That is how iron behaves. Haemoglobin can keep oxygen moving around your body while ferritin stores are depleted. The symptoms of that state are well described in clinical practice: persistent tiredness, hair shedding, restless legs, dizziness, cold hands and feet, breathlessness on exertion, and slow recovery after exercise.

Iron is needed well beyond red blood cells. It is used in muscle, in the brain and in the enzymes that generate energy, which is why depleted stores can affect how you feel long before anaemia appears on a blood count.

“Normal” laboratory range is not the same as optimal levels

Laboratories report a reference interval, not a target. Many UK laboratories only flag ferritin as low when it falls below roughly 15–30 µg/L. Clinical research, and clinicians who work with fatigue and hair loss, frequently note that symptoms of iron depletion appear when ferritin sits below 50–70 µg/L — comfortably inside the “normal” range on many reports.

Timing matters too. Ferritin is an acute-phase protein, so it rises with infection, inflammation, injury and hard training, and it can look reassuring when iron stores are in fact low. Results are best interpreted with your symptoms, your diet, any menstrual blood loss, and your other blood markers.

Standalone ferritin, or a wider energy panel?

Both routes are transparent about what is being measured.

• Ferritin — Iron Stores, £45. Measures ferritin specifically, the marker that reflects your stored iron.
• Ultimate Energy & Fatigue Panel. Adds Vitamin D, Active Vitamin B12 and a full thyroid profile (TSH, Free T4 and Free T3) alongside ferritin, covering the nutritional and thyroid factors most often associated with persistent tiredness.

If your tiredness comes with other general health concerns, the Complete Well Woman Screen includes ferritin with thyroid function, lipids, blood sugar and liver markers in one profile.

How OptiBlood home testing works

1. Order online. Choose your test, pay securely and your kit is dispatched to your door.
2. Collect at home. Your kit includes a CE/UKCA-marked finger-prick device, lancets, a collection tube and clear step-by-step instructions. Collecting the sample takes a few minutes.
3. Laboratory analysis. Samples are analysed by our partner laboratory, The Doctors Laboratory (TDL) — a UKAS-accredited medical laboratory (No. 8812) operating to ISO 15189:2022. Prepaid tracked return is included with every order.
4. Results in 24–72 hours. Your report arrives as a password-protected PDF by secure email, showing every result against its laboratory reference range.

Frequently Asked Questions

Why should I avoid iron supplements for 48 hours before testing?

Recent iron supplementation can raise ferritin and mask an underlying deficiency, so stop iron supplements for at least 48 hours before collection unless a clinician has advised otherwise. Continue any prescribed medication unless your doctor tells you to change it.

When is the best time to test ferritin?

Collect your sample in the morning where possible, and avoid testing during an active infection or within 48 hours of intense exercise, both of which can temporarily raise ferritin. Iron stores do not swing hour to hour, so a consistent morning sample gives a reliable reading.

Do I need a GP referral to check my ferritin?

No. You can order the test yourself, collect the sample at home and receive your results without a referral. If your ferritin is low, take the report to your GP or pharmacist, who can advise on the cause and on treatment.

Medical Disclaimer

OptiBlood tests provide laboratory information and are not a substitute for medical diagnosis, physical examination or emergency care. Discuss concerning results or symptoms with an appropriate healthcare professional.