Feeling persistently tired is easy to dismiss, particularly during pregnancy, while caring for a family or managing a busy working week. But when exhaustion comes with shortness of breath, dizziness, headaches, palpitations or looking noticeably pale, anaemia blood testing can provide a useful, evidence-based starting point. It helps a clinician understand whether your red blood cells are carrying enough oxygen around your body and, crucially, why they may not be.
Anaemia is common, but it is not one single condition. It is a finding with several possible causes, from low iron stores to vitamin deficiency, blood loss, inflammation or an inherited blood condition. The right tests and a thoughtful interpretation matter more than simply being told that your iron is “low”.
What does anaemia mean?
Anaemia occurs when you have too few healthy red blood cells, or when there is not enough haemoglobin inside them. Haemoglobin is the protein that carries oxygen from your lungs to the rest of your body. When levels are reduced, your organs and muscles may receive less oxygen than they need, which can leave you feeling drained or unable to do your usual activities comfortably.
Symptoms can develop gradually, so they are not always obvious. Some people notice a lack of energy, reduced exercise tolerance, brain fog, light-headedness, cold hands and feet, or breathlessness on stairs. Others have no symptoms at all and only discover anaemia through a routine blood test.
Symptoms alone cannot confirm anaemia. Tiredness has many possible explanations, including poor sleep, thyroid concerns, stress, infection and pregnancy itself. Blood testing gives your healthcare professional objective information to assess the bigger picture.
Anaemia blood testing: the tests that matter
A full blood count, often shortened to FBC, is usually the first test used to look for anaemia. It measures haemoglobin, red blood cell numbers and several features of the cells themselves. Together, these results can point towards the most likely type of anaemia.
Full blood count
Haemoglobin is a central result. A low level may indicate anaemia, although the reference range can differ by laboratory, age, sex and stage of pregnancy. The FBC also includes the mean cell volume, or MCV, which measures the average size of your red blood cells.
Small red blood cells can be seen in iron deficiency and in some inherited haemoglobin conditions, such as thalassaemia trait. Larger red blood cells may suggest a vitamin B12 or folate deficiency, though other causes are possible. Normal-sized cells do not rule out anaemia or explain its cause on their own, which is why further tests are sometimes needed.
Ferritin and iron studies
Ferritin measures the iron stored in your body. A low ferritin result is a strong indicator that iron stores are depleted, even before haemoglobin drops enough to cause anaemia. This makes ferritin particularly useful when someone has symptoms but a normal FBC.
Iron levels in the blood can vary during the day and may be affected by recent illness or inflammation. For that reason, clinicians do not usually rely on serum iron alone. They may assess ferritin alongside transferrin saturation, total iron-binding capacity and markers of inflammation where appropriate.
One important nuance is that ferritin can rise when the body is dealing with inflammation or infection. A ferritin result that appears normal does not always exclude iron deficiency in this situation. Your symptoms, medical history and the rest of your blood results should all be considered together.
Vitamin B12 and folate
Vitamin B12 and folate are needed to make healthy red blood cells. Deficiency may cause anaemia, but it can also affect the nervous system. Tingling, numbness, balance problems, memory changes or a sore tongue should be discussed promptly with a healthcare professional, especially if they are new or worsening.
Dietary intake can play a role, but it is not the only explanation. B12 deficiency may be linked to problems absorbing the vitamin, certain medicines or autoimmune conditions. This is why treating a result without exploring the cause may not be enough.
Tests tailored to your circumstances
Depending on your results and symptoms, a clinician may recommend additional investigations. These can include a reticulocyte count, which shows how actively your bone marrow is producing red blood cells, kidney or thyroid function tests, a blood film, coeliac screening or tests for inherited haemoglobin conditions.
If blood loss is suspected, the next steps will depend on your age, sex and medical history. Heavy periods are a frequent cause of iron deficiency in people who menstruate. Digestive symptoms, black stools, rectal bleeding or unexpected weight loss need medical assessment rather than self-treatment with iron alone.
Anaemia testing in pregnancy
Your blood volume changes significantly during pregnancy. Plasma increases more than red blood cells, creating a natural dilution effect that can lower haemoglobin readings. This is one reason pregnancy-specific reference ranges and clinical judgement are so valuable.
Iron requirements also rise as your baby grows and your body prepares for birth. Many pregnant women are offered blood tests at key points in pregnancy to check haemoglobin and identify issues that need support. Finding low iron stores early may help reduce symptoms and allow time for treatment to work before delivery.
Not every pregnant person with low iron will need the same approach. Your midwife, GP or obstetric team may advise dietary changes, oral iron, further testing or, in some circumstances, specialist treatment. Iron supplements can cause constipation, nausea and stomach discomfort, so it is worth discussing the dose and timing if they are difficult to tolerate. More is not always better, and supplements should not replace investigating significant or persistent symptoms.
If you are pregnant and experience chest pain, severe breathlessness at rest, fainting, heavy bleeding, a racing heart that does not settle, or feel acutely unwell, seek urgent medical help. These symptoms should not wait for a routine appointment.
Preparing for your appointment
Most anaemia blood tests are straightforward and only take a few minutes. You will usually not need to fast, although your healthcare provider will tell you if any tests included in your appointment have different instructions. Being well hydrated can make blood collection easier.
Before your appointment, make a note of your symptoms and when they started. It is also useful to share whether you have heavy periods, are pregnant or recently gave birth, follow a vegetarian or vegan diet, have digestive concerns, have had surgery affecting your stomach or bowel, or take regular medicines and supplements. These details can help make the interpretation of your results more accurate.
If you already take iron, B12 or folic acid, mention it. Supplements can influence results, and your clinician can advise whether any changes are needed before testing. Do not stop prescribed medication unless a healthcare professional has told you to do so.
What happens after your results?
A result outside the laboratory range is not automatically a reason to panic, and a result within range does not always explain every symptom. Good care looks at the pattern: your blood count, iron stores, medical history, pregnancy status, symptoms and any relevant previous tests.
Where iron deficiency is confirmed, treatment commonly includes identifying and addressing the cause alongside replacing iron. If low B12 or folate is found, treatment will be tailored to the deficiency and its likely source. Follow-up testing may be recommended to check that haemoglobin and stores are improving as expected.
At Miracle Scan, blood testing can be a convenient part of a wider, compassionate health assessment for women and men. Whether you are seeking reassurance during pregnancy or answers for ongoing tiredness, timely testing can help you take the next appropriate step with clarity.
You do not need to wait until fatigue becomes your new normal. If your energy, breathing or wellbeing has changed, speaking with a qualified healthcare professional and arranging the right blood tests can turn an uncertain symptom into a clearer plan for care.