Vitamin D is crucial for calcium absorption, bone health, immune function, and muscle strength. It is synthesized in the skin upon exposure to sunlight and is also found in foods like oily fish, fortified cereals, and dairy products. In the UK, limited sunlight exposure, especially during winter months, can lead to widespread vitamin D insufficiency. ​

When Low:

Vitamin D deficiency can result in bone disorders such as rickets in children and osteomalacia in adults, leading to bone pain and muscle weakness. Other symptoms include fatigue, frequent infections, depression, and impaired wound healing.Risk factors for deficiency include limited sun exposure, darker skin tones, obesity, and certain medical conditions affecting absorption.

When High:

Excessive vitamin D levels, often due to over-supplementation, can lead to hypercalcemia, characterized by nausea, vomiting, weakness, and kidney problems. It's important to monitor vitamin D intake and consult healthcare providers before taking high-dose supplements.​

Folate (vitamin B9) is important for DNA synthesis, red blood cell production, and fetal development.

When Low:

Linked to anemia, fatigue, irritability, and in pregnancy, neural tube defects. Often due to poor diet, alcohol use, or malabsorption.

When High:

Usually from supplementation. Excessive levels may mask vitamin B12 deficiency, potentially leading to neurological problems.

The HbA1c test measures the average blood glucose levels over the past two to three months. It reflects how much glucose is attached to haemoglobin in red blood cells. This test is commonly used to diagnose and monitor diabetes.​

When Low

A low HbA1c level may indicate episodes of hypoglycaemia (low blood sugar), which can cause symptoms like dizziness, sweating, and confusion. It may be a sign of overly aggressive diabetes treatment or other health conditions affecting blood sugar levels.​

When High

A high HbA1c level suggests poor blood sugar control, indicating a higher risk of diabetes-related complications such as nerve damage, kidney disease, and cardiovascular issues.

FT4 measures the unbound, active form of thyroxine in the bloodstream. It is essential for metabolism, growth, and development.

When Low:

Low FT4 levels are seen in hypothyroidism, where the thyroid is underactive. Symptoms can include fatigue, weight gain, depression, cold intolerance, and dry skin.

When High:

High FT4 levels indicate hyperthyroidism, where the thyroid is overactive. Symptoms include rapid heartbeat, weight loss, nervousness, sweating, and difficulty sleeping.

FT3 is the active form of thyroid hormone that helps regulate many body processes. It is often measured to assess thyroid function, particularly in suspected cases of hyperthyroidism.

When Low:

Low FT3 may point to hypothyroidism or non-thyroidal illness (a condition where severe illness affects thyroid function without primary thyroid disease). Symptoms include fatigue, slow metabolism, constipation, and sensitivity to cold.

When High:

High FT3 levels are typically seen in hyperthyroidism. Symptoms include anxiety, tremors, palpitations, weight loss, and heat intolerance.

Haemoglobin is a protein in red blood cells responsible for transporting oxygen throughout the body. Adequate haemoglobin levels are essential for maintaining energy and overall health.​

When Low

Low haemoglobin levels, or anaemia, can lead to fatigue, weakness, and shortness of breath. Causes include nutritional deficiencies, chronic diseases, or blood loss.​

When High

Elevated haemoglobin levels may result from living at high altitudes, smoking, or conditions like polycythaemia vera.This can increase the risk of blood clots and related complications.​

Haematocrit measures the proportion of red blood cells in the blood. It helps assess the blood's capacity to carry oxygen and can indicate hydration status.​

When Low:

A low haematocrit level suggests anaemia, leading to symptoms like tiredness and dizziness. It may result from blood loss, nutritional deficiencies, or chronic illnesses.​

When High:

High haematocrit levels can occur due to dehydration or conditions that increase red blood cell production. This may thicken the blood, raising the risk of clotting issues.

The red cell count indicates the number of red blood cells in the blood, which are crucial for oxygen transport. This test helps diagnose various conditions, including anaemia and polycythaemia.​

When Low:

A low red cell count can cause fatigue and weakness, often due to anaemia from factors like iron deficiency or chronic disease.​

When High:

An elevated red cell count may be a response to low oxygen levels or disorders like polycythaemia vera, potentially leading to increased blood viscosity and clotting risks.​

MCV measures the average size of red blood cells, aiding in classifying types of anaemia.​

When Low:

Low MCV indicates microcytic anaemia, often caused by iron deficiency or chronic disease, leading to symptoms like fatigue and pallor.​

When High:

High MCV suggests macrocytic anaemia, which may result from vitamin B12 or folate deficiencies, causing fatigue and neurological symptoms.​

MCH calculates the average amount of haemoglobin per red blood cell, providing insight into the cell's oxygen-carrying capacity.​

When Low:

Low MCH indicates hypochromic anaemia, commonly due to iron deficiency, leading to symptoms like tiredness and weakness.​

When High:

High MCH may be associated with macrocytic anaemia, often resulting from vitamin B12 or folate deficiencies, causing fatigue and cognitive disturbances.​

RDW assesses the variation in red blood cell sizes, aiding in diagnosing different types of anaemia.​

When Low:

A low RDW is generally not clinically significant and often indicates uniform red blood cell size.​

When High:

High RDW suggests a mix of red blood cell sizes, which can occur in iron deficiency anaemia or vitamin B12/folate deficiencies, leading to fatigue and weakness.​

Platelets are cell fragments essential for blood clotting, preventing excessive bleeding.​

When Low:

Low platelet counts (thrombocytopenia) can lead to easy bruising, prolonged bleeding, and are associated with conditions like immune thrombocytopenia or bone marrow disorders.​

When High:

High platelet counts (thrombocytosis) may increase the risk of clotting events and can be reactive (due to inflammation) or primary (due to bone marrow disorders).​

MPV measures the average size of platelets, providing information about platelet production in the bone marrow.​

When Low:

Low MPV indicates smaller platelets, which may be associated with conditions like aplastic anaemia or certain inherited disorders, potentially leading to bleeding issues.​

When High:

High MPV suggests larger, more reactive platelets, often seen in conditions like immune thrombocytopenia.

WBC measures the total number of white blood cells, which are crucial for fighting infections and regulating the immune system. It’s a core component of a complete blood count (CBC).

When Low:

Leukopenia may be due to bone marrow disorders, autoimmune diseases, or severe infections. It increases susceptibility to infections.

When High:

Leukocytosis is usually caused by infection, inflammation, trauma, or certain cancers like leukemia.

Iron is a vital mineral necessary for producing haemoglobin, the protein in red blood cells that carries oxygen. Adequate iron levels are essential for energy production and overall health.​

When Low:

Iron deficiency can lead to anaemia, causing symptoms like fatigue, weakness, and shortness of breath. Common causes include poor dietary intake, blood loss, or increased demand during pregnancy.​

When High:

Excessive iron levels may result from conditions like haemochromatosis, leading to joint pain, fatigue, and organ damage if untreated .​

TIBC measures the blood's capacity to bind iron with transferrin, reflecting iron transport availability.​

When Low:

Low TIBC can indicate chronic diseases, malnutrition, or iron overload conditions like haemochromatosis.​

When High:

Elevated TIBC is often seen in iron deficiency anaemia, where the body increases transferrin production to maximize iron transport .​

UIBC measures the reserve capacity of transferrin to bind more iron, helping assess iron metabolism.​

When Low:

Low UIBC suggests high iron saturation, possibly due to iron overload disorders.​

When High:

High UIBC indicates low iron levels, as seen in iron deficiency anaemia, reflecting increased transferrin availability.​

Transferrin saturation calculates the percentage of transferrin bound with iron, providing insight into iron availability.​

When Low:

Low transferrin saturation is indicative of iron deficiency, leading to anaemia and associated symptoms.​

When High:

High transferrin saturation may point to iron overload conditions, necessitating further evaluation and management.​

Ferritin is a protein that stores iron in your cells and releases it when needed. It reflects the body's iron reserves and is often the first indicator of iron deficiency or overload.

When Low: Indicates depleted iron stores, often seen in iron deficiency anemia. Symptoms can include fatigue, weakness, and hair loss.

When High: May suggest iron overload (e.g., hemochromatosis), inflammation, liver disease, or chronic illness. High levels in the absence of infection or inflammation should be further evaluated.

TSH is produced by the pituitary gland and regulates the production of thyroid hormones (T3 and T4) from the thyroid gland. It is a key marker for diagnosing thyroid disorders.

When Low:

Low TSH often indicates hyperthyroidism, where the thyroid is overactive. Symptoms may include irritability, insomnia, palpitations, and weight loss.

When High:

High TSH typically indicates hypothyroidism, where the thyroid is underactive. Symptoms include tiredness, weight gain, depression, slow heart rate, and feeling cold.

Monocytes are white blood cells that digest pathogens and damaged cells. They are part of the body's first line of defense.

When Low:

May be caused by bone marrow suppression or severe infections. It can reduce the body’s ability to respond to infection.

When High:

High monocytes can signal chronic infections, inflammatory conditions, or autoimmune diseases.

Indicates monocytes as a proportion of total white blood cells. It helps detect immune and inflammatory activity.

When Low:

May reflect bone marrow suppression or an acute immune reaction.

When High:

Suggests chronic infection, inflammation, or hematologic diseases.

Eosinophils help fight parasites and are involved in allergic reactions. They play a key role in inflammation and asthma.

When Low:

A low count is often normal but may also be seen during steroid use or stress responses.

When High:

High eosinophils can suggest allergies, asthma, parasitic infections, or certain cancers.

Indicates eosinophils as a percentage of the total white blood cell count. It helps assess allergic or parasitic activity.

When Low:

May reflect stress, acute infections, or use of corticosteroids.

When High:

Suggests conditions like asthma, hay fever, eczema, or parasitic infections.

Lymphocytes are white blood cells critical to the immune system, particularly in fighting viral infections. They include T cells, B cells, and natural killer cells.

When Low:

Lymphopenia may result from autoimmune diseases, corticosteroid use, or infections like HIV. It weakens the immune response.

When High:

Elevated lymphocytes often indicate viral infections, certain bacterial infections, or chronic lymphocytic leukemia.

This measures lymphocytes as a proportion of the total white blood cells. It's useful in evaluating immune function.

When Low:

May occur in acute stress, bacterial infections, or following chemotherapy.

When High:

Suggests chronic viral infection or lymphocytic leukemia.

Neutrophils are the most abundant white blood cells and are essential in fighting bacterial infections. They are the first responders to inflammation.

When Low:

Neutropenia may result from bone marrow problems, chemotherapy, or viral infections. It increases the risk of serious infections.

When High:

Elevated neutrophils typically indicate bacterial infection, physical or emotional stress, or inflammation.

This is the proportion of neutrophils among total white blood cells. It’s useful in evaluating acute infections or inflammation.

When Low:

May occur in viral infections or with bone marrow suppression.

When High:

Often seen in bacterial infections, stress, or chronic inflammation.

Basophils are a type of white blood cell involved in allergic reactions and inflammatory responses. They release histamine and other chemicals during immune responses.

When Low:

Low basophil counts are generally not concerning and may be a normal variation. They can also occur with stress or infections.

When High:

High basophils may be associated with allergies, chronic inflammation, or myeloproliferative disorders like chronic myeloid leukemia.

This represents the proportion of basophils relative to total white blood cells. It helps assess allergic and immune responses.

When Low:

A low percentage is typically not clinically significant. Basophils naturally occur in low numbers.

When High:

Elevated basophil percentage may point to chronic allergic reactions, parasitic infections, or hematological disorders.

Measures the bioavailable form of vitamin B12 that is actively used by the body. Important for red blood cell formation, nerve function, and DNA synthesis.

When Low:

Suggests B12 deficiency, even if total B12 appears normal. May lead to fatigue, nerve issues, or cognitive impairment.

When High:

Typically not harmful but can sometimes indicate liver disease or certain blood conditions.