What Is Biological Age and How to Measure It

The age on your passport is not the age that matters

You know your chronological age — the number of years since you were born. But two people born on the same day can have dramatically different health trajectories. One might have the cardiovascular system of someone ten years younger. The other might have the metabolic profile of someone a decade older.

The difference is biological age: a measure of how well your body is actually functioning, independent of the calendar.

How biological age is calculated

There is no single test for biological age. Instead, it is estimated using a combination of biomarkers that reflect organ function, inflammation, metabolic health, and cellular ageing.

The most common approaches include:

Blood biomarker algorithms

These use panels of 10-30 blood markers to estimate biological age. The most validated include:

• PhenoAge (Levine et al., 2018): Uses albumin, creatinine, glucose, CRP, lymphocyte percentage, mean cell volume, red cell distribution width, alkaline phosphatase, and white blood cell count. It predicts mortality and disease risk better than chronological age alone.
• GrimAge: Incorporates DNA methylation data to estimate biological age with high accuracy. It is one of the strongest predictors of lifespan and healthspan.

Simpler algorithms use routine blood markers — glucose, HbA1c, lipids, liver enzymes, inflammatory markers — to build a composite score that approximates biological age.

DNA methylation clocks

Epigenetic clocks measure chemical modifications to your DNA that change with age. The Horvath clock (2013) was the first widely used epigenetic clock. Since then, more advanced versions like GrimAge and DunedinPACE have improved accuracy.

These tests require specialised lab analysis and cost between $200-$500 per test.

Functional markers

Some researchers use functional tests — grip strength, VO2 max, walking speed, cognitive processing — as proxies for biological age. These are simple, free, and surprisingly predictive.

What makes biological age increase faster

Several modifiable factors accelerate biological ageing:

Chronic inflammation. Measured by hsCRP and interleukin-6. Persistent low-grade inflammation — from poor diet, excess visceral fat, chronic stress, or poor sleep — accelerates every ageing pathway.

Insulin resistance. Elevated fasting insulin and HOMA-IR indicate that your cells are struggling to respond to insulin. This drives metabolic dysfunction, increases oxidative stress, and accelerates cellular ageing.

Poor sleep. Consistently sleeping fewer than 7 hours accelerates telomere shortening and increases inflammatory markers. Sleep is not optional for longevity.

Nutrient deficiencies. Low vitamin D, low magnesium, and low omega-3 levels are independently associated with faster biological ageing.

Physical inactivity. Regular exercise — especially zone 2 cardio and resistance training — is the single most powerful intervention for slowing biological ageing.

How to reduce your biological age

The interventions with the strongest evidence:

1. Optimise metabolic health. Target fasting glucose below 4.8, HbA1c below 5.2%, and HOMA-IR below 1.0.
2. Reduce inflammation. Target hsCRP below 0.5 mg/L through diet, exercise, and stress management.
3. Exercise consistently. 150 minutes of zone 2 cardio plus 2-3 resistance sessions per week.
4. Sleep 7-9 hours. Prioritise sleep consistency over duration.
5. Correct deficiencies. Maintain vitamin D at 50-70 ng/mL, ferritin at 40-100 ng/mL, and omega-3 index above 8%.

Tracking your biological age with Gemut Health

Gemut Health calculates an estimated biological age from your blood test results using a validated biomarker algorithm. Each time you upload a new panel, your biological age is recalculated, letting you see whether your interventions are working.

Your biological age is not fixed. It responds to what you do. The first step is measuring it.