Add-on · Minerals

Red cell selenium test in the UK

A red cell selenium test measures selenium inside your red blood cells, reflecting your intake over recent months. Selenium is needed to convert thyroid hormone into its active form, for the body's main antioxidant enzymes and for sperm health. UK intakes are often on the low side, and too much is harmful. You can add red cell selenium to TrueVitals Ultimate for £79.

Add to Ultimate: £79Read with: Full thyroid panelSample: Clinic or home visitMain report: 4 working days

Add to Ultimate: £478 Compare panels

Add red cell selenium to Ultimate

Add-ons are tested on the same blood draw as your panel and reported inside your clinician-reviewed report, read alongside your other 140 results. They are not sold on their own.

Ultimate + red cell selenium, partner clinic

£478£399 + £79 add-on

Blood draw at a partner clinic included.

Choose clinic

Ultimate + red cell selenium, home visit

£507£399 + £29 visit + £79

A nurse comes to your home or workplace.

Choose home visit

Pay in instalments with Klarna or Clearpay at checkout. Want it with Advanced instead? Email support@truevitals.co.uk and we will set it up.

What selenium does

Selenium is built into proteins called selenoproteins. They include the enzymes that turn T4 into active T3 in the thyroid and other tissues, and glutathione peroxidase, one of the body's main antioxidant defences. Selenium also supports immune function and normal sperm.

The amount in food depends on the soil it was grown in, and UK and European soils are relatively low, so UK intakes often sit below the recommended level.

Who it is worth testing for

Thyroid questions, particularly raised thyroid antibodies (Hashimoto's), where selenium status is relevant.
Vegans and people who eat little fish, eggs or meat.
Gut conditions or weight-loss surgery that reduce absorption.
Male fertility, as part of a wider check.
People taking selenium or eating Brazil nuts daily, to avoid excess.

Low and high

Low red cell selenium

Low intake (common in the UK)
Plant-based diets
Malabsorption

High

Supplements on top of a good diet
Several Brazil nuts a day
Too much can cause hair loss, brittle nails, a garlic smell on the breath and nerve symptoms

How it fits with your other results

Ultimate includes TSH, free T4, free T3 and both thyroid antibodies (TPO and thyroglobulin). Reading selenium alongside them shows whether low selenium could be playing a part in how well you convert T4 to T3.

Where to get a selenium test in the UK

Option	Includes it	Price	What else you get
Ultimate + red cell selenium	Yes	£478 incl. clinic draw (home visit £507)	Read alongside TSH, free T4, free T3, TPO and thyroglobulin antibodies. Clinician-reviewed report.
TrueVitals Advanced	On request	£319 + £79	Includes TSH, free T4 and free T3; selenium can be added by email.
NHS GP	On request	Free if clinically indicated	Rarely tested outside specialist care.

TrueVitals prices checked 5 November 2026. Every TrueVitals report is clinician-reviewed. Pay in instalments with Klarna or Clearpay. Book a draw at one of 103 partner clinics, or add a home visit.

Be honest with yourself about what this test is for

A note on supplements: more is not better with selenium. The UK guide upper level for long-term intake is 350 micrograms a day from all sources, and a single Brazil nut can contain a large share of that. Test before supplementing for long periods.

A private panel is a good way to get a baseline, understand a result in context and track it over time. It does not replace your GP for symptoms, and anything that needs follow-up is flagged in plain words in your report.

Read alongside

Red cell selenium on its own rarely tells the whole story. In TrueVitals panels it is reported with these related markers:

TSHFree T4 and free T3Thyroid antibodies Red cell zincFull blood counths-CRP

Frequently asked questions

Is selenium included in Ultimate?

No. Ultimate includes the full thyroid panel with both antibodies. You can add red cell selenium for £79.

Does selenium help Hashimoto's?

Some studies show selenium lowers thyroid antibody levels, especially where intake is low. It is not a treatment on its own, and checking your level first avoids taking more than you need.

Can you have too much selenium?

Yes. Long-term high intake can cause hair loss, brittle nails, a garlic smell on the breath, skin problems and nerve symptoms.

Are Brazil nuts a good source?

They are very rich in selenium, but the amount varies hugely between nuts. One or two a day is usually plenty; eating many every day can push intake too high.

Can I add more than one mineral?

Yes. Email support@truevitals.co.uk and we will set up an order with several add-ons.

When will my result arrive?

Some specialist add-ons are sent on to a reference laboratory. Your main report arrives within 4 working days, and if an add-on result comes back later it is added to your report automatically and we let you know.

How this page was written: by James Smillie, founder of TrueVitals, reviewed by the TrueVitals clinical review team, using NHS and laboratory reference sources. Ranges are typical values; your report uses your lab's own ranges. TrueVitals sells the panels named on this page, so we have stated plainly what this test cannot do. Last updated 5 November 2026.

Check selenium with your thyroid

Ultimate + red cell selenium: £478 including the clinic draw, or £507 with a home visit. Clinician-reviewed report.

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