Helvy
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Thyroid
In the UK, the standard clinical (NHS) reference range for TSH (Thyroid Stimulating Hormone) is 0.4-4.0 mIU/L, with 1.0-2.0 mIU/L considered the performance-optimised range. A result within these ranges suggests typical status; only a qualified clinician can interpret an individual reading.
Thyroid stimulating hormone is produced by the pituitary gland and signals the thyroid to produce T3 and T4 — the hormones that regulate metabolism, energy production, and body temperature. TSH operates on an inverse relationship: high TSH indicates the thyroid is underperforming (hypothyroidism), while low TSH suggests overactivity (hyperthyroidism).
Optimal range · UK
1.0-2.0 mIU/L
Performance-optimised band · clinical (NHS) range 0.4-4.0 mIU/L
Reference ranges for TSH, not a personal result. Any individual reading should be interpreted by a qualified clinician.
Optimal ranges
| Range | Value |
|---|---|
| Clinical (NHS) reference range | 0.4-4.0 mIU/L |
| Performance-optimised range | 1.0-2.0 mIU/L |
The clinical range defines what is considered medically “normal” — broad enough to cover 95% of the population. The performance range reflects where research and clinical experience suggest most people feel and function at their best. A result in either range suggests typical status and is not a diagnosis; any individual reading should be interpreted by a qualified clinician.
Why it matters
The thyroid is the body's metabolic thermostat. Even mildly elevated TSH — subclinical hypothyroidism — can cause fatigue, weight gain, cold intolerance, and depression that is frequently misattributed to ageing or overtraining. For men, thyroid dysfunction also impacts testosterone production and cardiovascular health. Standard clinical ranges for TSH are very broad (0.4-4.0 mIU/L), meaning you can be symptomatic at 3.5 and be told everything is 'normal'. Functional optimisation aims for a tighter range where most people feel their best.
Symptoms
Low / Deficiency
High / Excess
Dietary sources
Supplementation
Selenium (200 mcg/day as selenomethionine) is the most evidence-based thyroid support nutrient — essential for T4 to T3 conversion and thyroid peroxidase function. Iodine supplementation (150-300 mcg/day) only if deficiency is confirmed — excess iodine can worsen thyroid conditions. Zinc (15-30 mg/day) supports thyroid hormone synthesis. Avoid soy isoflavones and excessive cruciferous vegetables if thyroid function is compromised. If TSH is persistently above 4.0, GP referral is recommended.
Testing
TSH is measured from a blood sample. With Helvy, that means a finger-prick kit taken at home and posted to a UKAS-accredited UK laboratory, with results in around 5 days, reviewed by a qualified clinician. Your result is reported against both the clinical range (0.4-4.0 mIU/L) and the performance-optimal range (1.0-2.0 mIU/L), so you can see not just whether you are “normal” but whether you are optimal. If you make a change, retest after 8-12 weeks to confirm it worked.
Research
Selenium supplementation in patients with autoimmune thyroiditis
Toulis KA, Anastasilakis AD, Tzellos TG, et al.
Thyroid (2010)
DOI: 10.1089/thy.2009.0351Test for this
The everyday baseline, 17 biomarkers covering thyroid (TSH and Free T4), cortisol, vitamin D, B12, magnesium, the full cholesterol panel, inflammation (CRP), and core liver and kidney markers.
A deep look at thyroid function (TSH, Free T4 and Free T3) alongside your liver, kidney and full cholesterol markers, 16 in total.
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This content is for educational purposes only and does not constitute medical advice. Your data suggests areas for optimisation, but any concerns should be discussed with a qualified healthcare professional. If your results flag values outside safe ranges, we recommend consulting your GP.
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