Mitochondrial Dysfunction: What We Know and What Actually Helps

If you have ever run out of energy halfway through the afternoon, it is tempting to think your “cellular batteries” are fading. The image is intuitive, but it can also mislead. Fatigue does not diagnose mitochondrial dysfunction, and a mitochondrion is not a battery that one supplement can recharge.

Mitochondria transform energy from nutrients, help manage calcium, participate in immune signalling and contribute to decisions about repair, adaptation and cell death. Their function changes with age and across many diseases. This is why mitochondrial dysfunction appears among the hallmarks of ageing. It is important biology, not one explanation for every symptom.

What a mitochondrion does, without turning it into a battery

On its inner membrane, groups of proteins transfer electrons and establish a proton gradient. ATP synthase uses that gradient to produce ATP, a molecule that enables cellular work. This process is connected to the use of fat, carbohydrate and amino acids, and varies with tissue, exercise, food intake and health.

Mitochondria also form networks that fuse, divide and move. Damaged parts can be isolated and recycled through mitophagy. They produce reactive oxygen species too. In excess these can contribute to damage, but controlled amounts act as adaptation signals. The real story is not “free radicals are bad”; it is about dose, location and timing.

What changes with age

The 2023 hallmarks review describes changes in energy production, quality control, communication between organelles and inflammation. A clinical review by Miwa and colleagues also explains the two-way relationship with cellular senescence. Altered mitochondria can promote stress signals, while a senescent cell can remodel its mitochondrial network. That connection does not prove that correcting one molecule will stop ageing.

Process	What may change	Why it matters
Fission and fusion	The network may lose flexibility to adapt or separate damaged parts.	Quality matters as much as quantity.
Mitophagy	Recycling can become less efficient in some tissues and settings.	Poorly functioning components may accumulate.
Redox signalling	An adaptive signal may spill over into persistent damage.	This is why removing every oxidant is not the answer either.
Cellular communication	Signals to the nucleus, immune system and metabolism can change.	Mitochondria work inside a network, not alone.

Language matters. People do not age identically, and tissues within one person do not change at the same pace. Even the supposed universal decline in NAD+ needs qualification. A seven-cohort human study published in 2026 found that whole-blood NAD+ remained stable with age and several lifestyle interventions. This does not rule out changes in specific tissues; it shows that a blood sample does not automatically represent muscle, liver or brain. The link with sirtuins also depends on tissue and outcome.

Two conversations that should not be mixed

Situation	What it means	Next step
Age-associated changes	Patterns observed in tissues, models and populations, without one diagnostic threshold.	Work on physical capacity, sleep, nutrition and cardiometabolic risk.
Fatigue or slow recovery	Real symptoms, but highly non-specific.	History, examination and tests guided by likely causes.
Mitochondrial disease	A heterogeneous group of disorders that can affect muscle, brain, heart, vision, hearing and other systems.	Specialist assessment, sometimes including genetic, metabolic or tissue testing.

The Mitochondrial Medicine Society consensus makes clear that specialist diagnosis combines clinical presentation, family history and selected investigations. It does not come from a wellness panel. Progressive weakness, ptosis, seizures, episodes of rhabdomyolysis, cardiomyopathy or several affected organs deserve medical priority.

How a complaint of “low energy” is investigated

The first layer is usually unglamorous and genuinely useful: sleep, medication, mood, food intake, alcohol, training load and accompanying symptoms. Depending on the history, blood tests may look for anaemia, thyroid disturbance, glucose problems, nutritional deficiencies, inflammation, infection, or kidney or liver disease. The list changes with the person.

Next, function can be measured. Strength, walking speed and exercise tolerance describe what the body can do. VO2 max integrates ventilation, heart function, oxygen transport, circulation and muscle. Its association with health and mortality is strong, but calling it a “mitochondrial test” erases all those links in the chain.

Lactate, respiratory-chain studies, muscle biopsy, genetics or metabolomics may be appropriate in specific scenarios. A normal lactate does not exclude every mitochondrial disease, and a raised result does not confirm one. Likewise, plasma CoQ10, urinary oxidative damage, mitochondrial DNA copy number or an NAD+/NADH ratio cannot summarise the body's energetic state.

What can genuinely help

Aerobic and strength exercise

Muscle retains substantial capacity to adapt across much of life. Aerobic training increases oxidative demand; strength training protects mass, power and glucose handling. Recent reviews describe changes in biogenesis, dynamics and mitophagy. In a person, the useful result is checked through tolerance, performance, recovery and metabolic health, not through a promise to “make new mitochondria”.

More is not always better. A training load that rises too quickly can worsen fatigue or pain. Cardiovascular disease, frailty or unexplained symptoms change the starting point. Progression and recovery are part of the intervention.

Sleep, nutrition and metabolic context

Poor sleep, low energy availability, excess alcohol or poor metabolic control impair the ability to train and recover. Correcting these factors is not a “mitochondrial therapy”, but it creates the context in which muscle and other tissues can adapt. A molecular label does not improve a basic intervention; it only makes it sound more sophisticated.

NAD+, CoQ10, carnitine and other supplements

These molecules participate in real processes. The clinical question is harder: in which population, at what dose, for how long and with what benefit? NAD+ precursors can raise metabolites in some trials without demonstrating general mitochondrial rejuvenation. CoQ10 and carnitine have roles in deficiencies or specific medical settings; that does not make them a universal answer to fatigue.

A total war on oxidants also deserves caution. In one randomised trial, high-dose vitamins C and E blunted some cellular adaptations to endurance training, although they did not erase every performance improvement. It is a useful reminder: a biological signal can be harmful in excess and helpful at an appropriate dose.

A more honest way to talk about mitochondria

A good explanation does not promise abstract “cellular energy”. It names the tissue, method and outcome. Was a protein measured in mice, respiration measured in a muscle biopsy, NAD+ measured in blood, or stair-climbing capacity measured in a person? Each answer sits on a different evidence rung.

The practical idea is reassuring: protect the capacity you can observe, investigate persistent symptoms and reserve complex tests for concrete clinical questions. Mitochondria are fascinating. They do not need to become a vehicle for selling certainty.

Frequently asked questions

What is mitochondrial dysfunction?

It is an alteration in processes such as ATP production, reactive-species control, mitochondrial dynamics and recycling. The term describes biology and several diseases, not one diagnosis for fatigue.

Does fatigue mean my mitochondria are not working properly?

Not necessarily. Fatigue also occurs with anaemia, thyroid disorders, sleep apnoea, infections, medication, low energy intake, depression and many other conditions.

Is mitochondrial dysfunction the same as mitochondrial disease?

No. Mitochondrial diseases are heterogeneous clinical disorders, often genetic, that may affect several organs and require specialist assessment.

Is there a blood test for mitochondrial function?

There is no routine blood test that summarises mitochondrial function across the body. Lactate, metabolites, mitochondrial DNA or NAD+ answer specific questions and should not be interpreted alone.

Does VO2 max directly measure mitochondria?

No. VO2 max integrates lungs, heart, blood, circulation and muscle. It is a valuable measure of cardiorespiratory capacity, but it cannot locate a mitochondrial problem by itself.

Which intervention has the best support?

Progressive aerobic and strength exercise, adapted to the person, has the most consistent human support for improving physical capacity and remodelling mitochondrial processes.

Do NAD+, CoQ10 or carnitine rejuvenate mitochondria?

General rejuvenation has not been demonstrated in healthy people. Some compounds have specific indications or findings, but that does not make them a universal protocol.

When should I seek prompt medical advice?

Progressive weakness, marked exercise intolerance, ptosis, seizures, unexplained vision or hearing loss, rhabdomyolysis, cardiomyopathy, lactic acidosis or multisystem symptoms need medical assessment.

Sources

1. López-Otín C et al. Hallmarks of aging: an expanding universe. 2023.
2. Miwa S et al. Mitochondrial dysfunction in cell senescence and aging. 2022.
3. Somasundaram I et al. Mitochondrial dysfunction and its association with age-related disorders. 2024.
4. Parikh S et al. Consensus on diagnosis and management of mitochondrial disease. 2015.
5. Cai T et al. Exercise-mediated mitochondrial quality control remodeling in aging. 2026.
6. Trętowicz MM et al. Human whole-blood NAD+ levels do not vary with age or lifestyle interventions. 2026.
7. Paulsen G et al. Vitamin C and E supplementation and endurance-training adaptation. 2014.
8. Mandsager K et al. Cardiorespiratory fitness and long-term mortality. 2018.

This article is informational and does not replace medical assessment. Persistent fatigue, loss of capacity or multisystem symptoms need clinical context before supplements or protocols are started.