What is the Iodine (Serum) test?

The Iodine (Serum) test measures the concentration of iodine circulating in the bloodstream. Iodine is an essential trace element required for the production of thyroid hormones, which regulate metabolism, growth, and energy balance.

Adequate iodine intake is vital for normal thyroid function. Both iodine deficiency and excess can disrupt thyroid hormone synthesis, potentially leading to hypothyroidism or hyperthyroidism.

While urine iodine is often used for population-level assessment, serum iodine can provide useful insight in individual clinical and nutritional evaluations, especially when thyroid dysfunction is suspected.

Why do I need an Iodine (Serum) test?

Iodine imbalance can affect thyroid health, energy levels, and metabolic regulation. Testing helps identify deficiency or excess to guide appropriate intervention.

You may need a Serum Iodine test if you:

• Have thyroid dysfunction or abnormal thyroid tests
• Have symptoms of iodine deficiency or excess
• Follow a restricted or low-iodine diet
• Avoid dairy, seafood, or iodised salt
• Are pregnant or planning pregnancy
• Have unexplained fatigue or weight changes
• Are assessing nutritional micronutrient status

Symptoms associated with iodine imbalance may include:

• Fatigue
• Weight gain or loss
• Cold or heat intolerance
• Neck swelling (goitre)
• Hair thinning
• Menstrual irregularities

Benefits of the Iodine (Serum) test

• Assesses iodine status
  Identifies deficiency or excess.
• Supports thyroid function evaluation
  Complements TSH, T3 and T4 testing.
• Useful in nutritional assessment
  Identifies micronutrient imbalance.
• Relevant in pregnancy planning
  Adequate iodine is essential for fetal development.
• Helps guide dietary adjustments
  Informs iodine intake optimisation.
• Clinically recognised trace element test
  Used in endocrine and nutritional medicine.
• Supports investigation of goitre
  Helps identify iodine-related causes.
• Simple blood test
  Requires only one sample.

Step by step – how the test works

You can access Serum Iodine testing UK-wide through two options:

1. Clinic appointment
   Attend your nearest UK clinic where a healthcare professional will take your blood sample.
2. At-home or hotel visit (£60 extra)
   A qualified phlebotomist comes to your home or hotel, so you don’t need to travel.

Your sample is analysed in an accredited UK laboratory, and results are delivered securely.

Your results explained

Low serum iodine levels

May indicate iodine deficiency, which can impair thyroid hormone production.

Typical UK interpretation:

• Below laboratory reference range

Normal serum iodine levels

Suggest adequate iodine status for thyroid hormone synthesis.

Typical UK interpretation:

• Within reference range

High serum iodine levels

May indicate excess iodine intake, which can also disrupt thyroid function.

Typical UK interpretation:

• Above laboratory reference range

Results should be interpreted alongside thyroid function tests and dietary history.