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.

TPEX (TPO antibodies) are markers of autoimmune thyroid disease. They target the enzyme involved in thyroid hormone production.

When Low:

Usually considered normal.

When High:

Indicates autoimmune thyroid conditions like Hashimoto’s thyroiditis or Graves’ disease.

Thyroglobulin Antibodies targets thyroglobulin, a protein involved in thyroid hormone production. It is another marker of autoimmune thyroid disorders.

When Low:

Normal levels suggest no autoimmune thyroid activity.

When High:

Suggests autoimmune thyroid diseases, particularly Hashimoto’s thyroiditis or, less commonly, Graves’ disease.

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.​

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.

CRP is a protein produced by the liver in response to inflammation. Measuring CRP levels helps detect acute and chronic inflammatory conditions and assess the risk of cardiovascular diseases.​

When Low:

Low CRP levels are normal and indicate the absence of significant inflammation in the body.​

When High:

Elevated CRP levels suggest the presence of inflammation due to infections, autoimmune diseases, or chronic conditions like heart disease. High-sensitivity CRP tests can help evaluate the risk of cardiovascular events. Persistent elevation warrants further investigation to identify and manage the underlying cause. ​

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.

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.

Measures the total amount of vitamin B12 in the blood, including both active and inactive forms.

When Low:

Indicates vitamin B12 deficiency, which can cause anemia, fatigue, neurological issues, and memory problems.

When High:

May not always be concerning but can suggest liver disease or supplementation. Needs to be interpreted with active B12 levels.