|🔎 PART 2/2 · A two-part series on biomarkers. Part 1 covers metabolic, cardiovascular, inflammation and organ function →

You know that feeling when your energy drops and you cannot quite explain why? 

You know that feeling when your energy drops and you cannot quite explain why? 

Or when you get enough sleep but still wake up feeling drained? 

Maybe recovery takes longer than it used to, or you just do not feel like yourself.

Most people notice these changes. Fewer realise that some of them can be traced back to measurable signals in the body.

The biomarkers in this guide are closely related to how you feel day to day. They can reveal changes in your hormones and whether your body has the nutrients it needs. They also offer clues about how you are ageing over time.

That is where the idea of optimisation becomes more practical. Once you can measure what is changing, you have a clearer starting point for understanding what may need attention.

"The point is to optimise all your parameters," says Dr Niko Mihic, Chief Medical Officer at Axo Longevity and medical supervisor at Real Madrid. "How can we be the best we can be?"

Hormonal biomarkers

What they tell you: How changes in your hormones may be affecting your energy, mood, sleep, recovery and libido.

Hormones influence far more of your day than most people realise. They affect how energised you feel in the morning, how well you recover, how you respond to stress and how your body changes with age.

When hormone levels shift, the effects can be easy to dismiss. You may feel more tired, sleep differently or notice that recovery takes longer, without immediately connecting those changes to something measurable.

• Thyroid hormones, including TSH, T3 and T4, help regulate the pace of your metabolism and influence energy throughout the body.

• Cortisol plays a central role in the stress response and follows a daily rhythm that affects energy and sleep. 

• DHEA also changes with age and is involved in several hormonal pathways.

Then there are the sex hormones. 

• Testosterone and oestrogen influence reproductive health, but their effects extend into areas such as muscle, bone health, mood and energy.

The important thing is how these hormones interact. A change in one can influence another, which is why looking at several together can provide more context than reading a single result on its own.

As Dr Mihic puts it, "You do the hormonal testing, and you see if there is a deficit of the hormones that are involved.”

Nutritional biomarkers

What they tell you: Whether your body has enough of the nutrients it needs to support energy, concentration and day-to-day function.

Sometimes feeling tired or run-down comes down to something surprisingly basic: your body may simply be missing what it needs.

That can be easy to overlook because nutrient deficiencies do not always cause one obvious symptom. You might notice lower energy, poorer concentration or changes in sleep without immediately linking them to a vitamin or mineral level.

• Vitamin D plays a role in bone and muscle health, immune function and the brain. Levels can vary widely between people and often fall during winter, particularly in countries with less sunlight.

Dr Mihic argues that context matters when interpreting a result.

Dr Mihic argues that context matters when interpreting a result.

“What’s the optimum value for vitamin D? Not for the general population, but for you,” he says. “Vitamin D is good for bones, for muscles. It’s also brain food. It passes the blood-brain barrier.”

• Vitamin B12 and folate support healthy nerve function and red blood cell production, while ferritin gives an indication of your iron stores. Low levels can contribute to tiredness and reduced exercise tolerance.
• Magnesium is involved in muscle and nerve function and plays a role in many processes linked to energy and recovery.

Once you measure what is happening, you have something concrete to work with.

For more on why an optimal level can be more useful than simply being within a “normal” range, see our guide to what a biomarker is.

Biological age and longevity biomarkers

What they tell you: How your body is changing with age and whether those changes may be happening faster or slower than expected.

You can be the same age as someone else and still feel completely different.

One person may recover well, sleep deeply and still feel mentally sharp. Another may notice that energy, resilience or recovery has started to shift.

Biological age tries to put a number around that difference.

Many of the biomarkers already covered in this series contribute to the picture. Blood sugar regulation, inflammation and hormone levels can all influence how the body changes over time. When you look at them together, they begin to show patterns that matter for long-term health.

There are also newer ways of estimating biological age more directly.

• Epigenetic clocks look at chemical changes to DNA that tend to shift with age.
• Glycan age looks at changes in immune-related proteins that are associated with inflammation and ageing.
• Telomere length offers another view by looking at the protective ends of chromosomes, although its use as a standalone measure of biological age is still being studied.

This is an evolving area of science, and no single test can tell you exactly how old your body is.

The value comes from tracking change over time and seeing whether the direction of travel is improving.

See what your biomarkers reveal

The biomarkers in this guide are only part of the picture. Axo Longevity measures more than 100+ across 36+ health areas, reads them against optimal ranges rather than just "normal", and turns your results into a personalised plan built around you.

Explore Axo Longevity's biomarker panel →

Frequently asked questions

1) What hormones should I get tested?
A useful baseline includes thyroid (TSH, Free T3, Free T4), cortisol, DHEA-S, and the sex hormones testosterone with SHBG and oestradiol. Which matter most depends on your age, sex, and symptoms.

2) Can a blood test show your biological age?
Not exactly, but newer biomarkers like epigenetic clocks and glycan age can estimate how fast your body is ageing. The science is still developing, so they are best used to track change over time rather than as a single definitive number.

3) Are nutrient deficiencies really that common?
Yes. Vitamin D, iron, B12, and magnesium are among the most common deficiencies worldwide, and fatigue is often the first sign. Many people have low levels without knowing it.

4) Why do I feel tired when my results look normal?
"Normal" reflects the average across a population, not what is optimal for you. A result can sit inside the normal range while still being low enough to affect your energy, mood, or sleep.

5) How often should I test these biomarkers?
:Once a year suits most people, though hormones and nutrient levels can be checked more often if you are actively working on them. The value is in tracking the trend, not a single reading.

Reference

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