Biological age tests in the UK: which type to choose

Biological age tests in the UK come in four types: DNA methylation (epigenetic) tests, glycan tests, blood marker tests and telomere length tests. They use different samples, from a cheek swab to a blood draw, and they measure different things, so two tests can give you two different ages. If you already have recent blood test results, you can work out a blood marker age for free with our biological age calculator.

What are the types of biological age test?

Type	What it measures	Sample	Published method
DNA methylation	Chemical tags (methyl groups) at set points on your DNA	Cheek swab, saliva or blood	Horvath clock (2013), GrimAge (2019), DunedinPACE (2022)
Glycan	Sugar chains attached to IgG antibodies in your blood	Finger-prick blood	Krištić and colleagues (2014)
Blood markers	9 routine blood results plus your age	A standard blood draw	PhenoAge, Levine and colleagues (2018)
Telomere length	The length of the protective ends of your chromosomes	Blood or saliva	Several lab methods, which don’t always agree

DNA methylation tests

These are the tests most people mean by “epigenetic age”. They read chemical tags at hundreds of set points on your DNA and feed them into a formula, called a clock. The first widely used clock was published by Steve Horvath in Genome Biology in 2013. Later ones include GrimAge (2019) and DunedinPACE (2022), which gives a pace of ageing instead of an age.

Ask which clock a test uses. Different clocks can give you different results from the same sample, so a test that names its clock is easier to compare. TruDiagnostic is one company that sells this type of test and ships to the UK.

Glycan tests

Glycan tests measure the sugar chains attached to IgG, a common antibody in your blood. The link between these sugars and age was described by Krištić and colleagues in 2014. The best known UK test of this type is GlycanAge, which uses a finger-prick sample you post back.

Blood marker tests (PhenoAge)

PhenoAge is a published formula, from Levine and colleagues in Aging in 2018. It uses 9 routine blood results: albumin, creatinine, glucose, C-reactive protein, lymphocyte percentage, mean cell volume, red cell distribution width, alkaline phosphatase and white blood cell count.

Most private “advanced” or “longevity” blood tests include all 9. NHS blood tests often leave out red cell distribution width or C-reactive protein. If you have the results, put them into our free PhenoAge calculator. It costs nothing, and nothing is sent anywhere.

Telomere length tests

Telomeres are the protective ends of your chromosomes. A telomere test gives you a length and compares it with other people your age. Different laboratory methods can give quite different lengths, so only compare results from the same laboratory.

How accurate are biological age tests?

Each one is accurate at what it measures, but they measure different things. That is why someone can get one age from a glycan test and another from an epigenetic test in the same week. Results can also move between tests a few weeks apart, so one result tells you less than a trend over time.

If you want to track change, pick one type of test, from one company, and repeat it at the same time of day, under similar conditions.

How to choose a biological age test

• Pick the type first: DNA methylation, glycan, blood markers or telomeres.
• Ask which published method the test uses, and whether it has changed since your last result.
• Check what sample it needs. A cheek swab is easier than a finger prick, and both are easier than a blood draw.
• Price up a repeat test as well as the first one, if you want to track change.
• Start with what is free: our biological age calculator and longevity test.

Can supplements change your biological age result?

I can’t tell you that any supplement changes a biological age result, and no seller in the UK should. Health claims for NMN aren’t authorised in Great Britain. I haven’t had an epigenetic test myself. If you take NMN and want to track a biological age result, our NMN trials tracker lists what the published human trials did measure.