Mitochondrial disease diagnosis

Getting a diagnosis of mitochondrial disease

Living with unexplained and often debilitating symptoms can be frightening. When the body’s unable to produce enough energy, it can have a significant impact on health, wellbeing and quality of life.

For some people, the answer is mitochondrial disease, often shortened to ‘mito’. Getting to that answer can take time, but there is a pathway and there’s support at every step. This page explains how mitochondrial disease is diagnosed in the UK.

If you’re early in the journey, you’re not alone. The Lily Foundation are here to support every patient, carer and loved one affected by a mitochondrial disease diagnosis.

First things first, what are mitochondria?

Mitochondria are present inside almost all our cells, turning food and oxygen into the energy your body needs. That energy powers everything, from your brain and heart to your muscles, hearing and digestion. When mitochondria don’t work properly, cells can struggle to produce energy, and that can lead to a condition called mitochondrial disease.

What is mitochondrial disease?

Mitochondrial disease is actually an umbrella term. It describes many different conditions that happen when the mitochondria in your cells can’t make enough energy.

Symptoms can appear across multiple different systems in the body, especially affecting those that require a lot of energy, such as the brain, heart or muscles.

When it comes to mitochondrial disease, everyone is affected differently, and two people with the same genetic change may have very different experiences. Some conditions appear in childhood, while others start in the teens or adulthood.

If you want a simple explainer to return to and share with family or your GP, our page on What is mitochondrial disease? is a good place to start.

What kinds of symptoms typically prompt investigation for mitochondrial disease?

Mitochondrial disorders can present at any age, but symptoms often differ between children and adults, reflecting how energy demand and organ involvement change across the lifespan. This variability is one of the reasons mitochondrial disease can be difficult to recognise and diagnose.

Symptoms in children

In children, mitochondrial disease often affects growth and development and may involve multiple organ systems from an early age. Symptoms may appear in infancy, early childhood or during periods of rapid development.

Common symptoms in children may include:

• Developmental delay or loss of previously acquired skills
• Low muscle tone (hypotonia) and weakness often affecting the trunk muscles
• High muscle tone (dystonia) affecting the limbs
• Feeding/swallowing difficulties and poor growth
• Seizures or epilepsy
• Movement disorders or poor co-ordination
• Vision or hearing problems
• Heart involvement, such as cardiomyopathy
• Recurrent or unexplained episodes of illness during infections

Because symptoms may evolve over time, some children are initially diagnosed with other neurological or metabolic conditions before mitochondrial disease is considered.

Symptoms in adults

In adults, mitochondrial disorders often present more gradually and may initially affect a single system, although multiple systems can become involved over time. Symptoms may first appear in adolescence or adulthood, even if the underlying genetic change has been present since birth.

Common symptoms in adults may include:

• Persistent fatigue or exercise intolerance
• Muscle weakness, cramps or pain
• Migraines or recurrent headaches
• Hearing loss or vision problems
• Gastrointestinal symptoms, such as ‘irritable bowel’, severe constipation and loss of appetite
• Diabetes or endocrine issues
• Neurological symptoms, including balance problems or peripheral neuropathy

Some adults experience relatively mild or non‑specific symptoms for many years, with many symptoms easily confused with other diseases or as a normal part of aging, which can delay referral for specialist assessment and genetic testing.

‘Red flag’ symptoms to watch for

Clinicians often look for patterns rather than a single symptom, and certain patterns can prompt a referral. These include:

• Symptoms in more than one organ system, for example muscle weakness plus hearing loss
• Unexplained neurological symptoms, such as seizures or stroke-like episodes, especially at a young age
• Developmental delay, failure to thrive, feeding difficulties or loss of skills in infants and children
• Multi-system involvement, for example cardiac issues, diabetes, gastrointestinal problems and temperature regulation difficulties, occurring together or in close sequence
• Persistent lactic acidosis in blood tests without another clear cause
• Family history of similar symptoms, sudden visual loss, hearing loss or unexplained early deaths
• Unexplained fatigue with exercise intolerance or muscle weakness that worsens after minor illness
• Vision changes such as painless, rapid vision loss in young adults (seen in LHON)

Having one or more of these ‘red flag’ symptoms is not an automatic diagnosis. If any of these seem familiar, keep a simple symptom diary and share it with your GP, along with your family history and any previous test results.

What are the first steps in getting a mitochondrial disorder diagnosis?

A GP is able to refer patients for further specialist testing based on their clinical symptoms, including access to genetic testing through the NHS, where clinically appropriate.

Depending on results, a patient may then be referred to a number of specialist teams depending on local provision and symptoms – this could be a neurologist, metabolic or genetics team. In some cases, referral to one of the NHS Highly Specialised Services may be recommended, so that patients can access the mitochondrial disease team and the research opportunities this brings.

How is mitochondrial disease diagnosed?

Diagnosis brings together clinical features and targeted investigations, with genetic testing now playing a central role in confirming many cases of mitochondrial disease.

What genetic tests are available for diagnosing mitochondrial conditions?

A specific genetic diagnosis is now central to diagnosis for mitochondrial disease. It can clarify prognosis, inform surveillance and treatment choices, guide eligibility for clinical trials and help families consider reproductive options. It also connects patients to the right research and support networks.

Gene panels targeting nuclear and mitochondrial DNA, and modern sequencing techniques, including whole genome sequencing, can identify the underlying variant in many patients. Mitochondrial DNA testing may be done in blood, urine or muscle.

In addition to genetic testing, doctors can use a range of other tests to help them diagnose mitochondrial disease.

You may not need all of the following, but here’s what’s commonly used:

Clinical assessment

Including medical history, family history and multi-system review.

Blood, urine and/or saliva tests

Checking full blood count, lactate, creatine kinase, liver enzymes, glucose control, thyroid function and specific metabolites. Urine organic acids and amino acids can hint at energy pathway issues.

Imaging

Children with neurological involvement may benefit from a brain MRI, which can show patterns suggestive of mitochondrial disease, such as changes in the basal ganglia or stroke-like lesions that do not follow a typical blood vessel territory. Cardiac imaging and echocardiography may be used if heart involvement is suspected or as part of an ongoing health surveillance for mitochondrial conditions where heart involvement can be anticipated.

Functional studies

ECG and Holter monitoring for rhythm problems, audiology for hearing, ophthalmology for the retina and optic nerve, and exercise testing in selected cases.

Muscle biopsy

Less common than it used to be, but still important in some scenarios. A small sample is examined for characteristic changes, enzyme activities and mitochondrial DNA content. Biopsy is considered when genetic testing is inconclusive or when tissue analysis will guide management.

Diagnostic innovation

The Lily Foundation invests in diagnostic innovation to complement NHS pathways. Our Precision Medicine Diagnostics project supports deeper analysis and reanalysis of genetic data using modern tools. This helps identify variants that are not easily detected using standard approaches and can open doors to research studies and tailored care.

This programme doesn’t replace NHS services – it sits alongside them, helping to close gaps, shorten the diagnostic odyssey and get families to answers sooner.

Why does a confirmed diagnosis of mitochondrial disease matter?

A precise diagnosis does more than put a name to symptoms. It can:

• Shape day-to-day management and surveillance for organ systems at risk
• Highlight safe versus potentially harmful medicines
• Enable access to natural history studies and clinical trials that match your gene or syndrome
• Inform family planning, including reproductive options that may reduce transmission risk

If you’re thinking about exploring reproductive choices, you can read more about mitochondrial reproductive options and we’d also encourage you to speak with your specialist team.

Who diagnoses mitochondrial disease?

In the UK, diagnosis is usually made within specialist services, based on a combination of clinical assessment, investigations and genetic testing, with the latter typically performed in one of three NHS Highly Specialised Diagnostic Services based in Newcastle, London and Oxford.

Patients are typically assessed by multidisciplinary teams, which may include neurologists, clinical geneticists and metabolic physicians. In situations where the diagnosis is not clear, a clinical opinion may be sought from a mitochondrial specialist through the NHS Highly Specialised Services or via Great Ormond Street Hospital.

These teams often work together with other specialists, such as cardiology, ophthalmology and audiology, to build a complete picture and confirm a diagnosis. For children, paediatricians with expertise in rare diseases play a central role in co-ordinating care.

How long does diagnosis take?

For most people who are clinically assessed at a specialist or highly specialised centre, the diagnosis of mitochondrial disease is fairly rapid. Rapid R14 Whole Genome Sequencing, for example, can provide a diagnosis within a week in extreme cases. Many mtDNA diagnoses will be evident from the clinical history and examination findings.

For others with very rare forms of mitochondrial disease, finding the exact genetic cause can be extremely challenging. Some people wait many months to years for scientists to identify theirs, especially when additional functional tests are required or international collaboration to join up clinicians and researchers working on confirming new forms of mitochondrial disease.

The diagnostic odyssey has been compared to looking for a needle in a haystack or a single spelling mistake in an entire dictionary, which is why it can sometimes be a lengthy process.

How accurate are commercial genetic tests for mitochondrial disease?

There are simple high street tests that claim to assess mitochondrial health and function. However, there’s no reliable over-the-counter test that can genetically diagnose mitochondrial disease, and there’s no evidence to recommend the use of these tests. Proper diagnosis combines clinical evaluation, laboratory tests and genetic analysis in a specialist setting.

What happens after a diagnosis?

A diagnosis of mitochondrial disease can bring clarity after a long diagnostic journey, but it often raises new questions about treatment, prognosis and day‑to‑day management. While there is currently no cure for mitochondrial disease, a confirmed diagnosis plays a crucial role in guiding care, monitoring health and offering support to individuals and families.

Access to support and resources

Even after diagnosis, there may be unanswered questions about how the condition will progress. Mitochondrial disease is highly variable, and predicting outcomes can be difficult. Ongoing follow‑up with specialist teams allows care plans to adapt as needs change.

After diagnosis, many people benefit from connecting with:

• Specialist mitochondrial disease centres
• Patient support organisations and charities like The Lily Foundation
• Rare disease networks

These resources can provide practical advice, emotional support and up‑to‑date information about research and clinical trials.

Here at The Lily Foundation, we understand the strength and power of community in helping to support patients and families facing a mitochondrial disease diagnosis.

Whether you’re a patient, parent, sibling or friend, we’re here to provide comprehensive mitochondrial disease support. Our resources and services are designed to help you manage the emotional, physical and practical aspects of a mitochondrial disorder, with a focus on improving quality of life.

If you’ve been diagnosed with mitochondrial disease and need to talk to someone, we’re here to listen. You can contact Liz by calling 0300 400 1234 or emailing [email protected]. Feel free to get in touch if you’re caring for someone with suspected or confirmed mitochondrial disease too.

We’re also available through our social media channels, where we closely monitor messages to respond as quickly as possible. Many members of The Lily Foundation team have direct experience with mitochondrial disease, which makes a meaningful difference in the support we can provide to families.

Finally, we’re proud to partner with Rareminds to offer a free, confidential counselling service for patients and family members aged 18+ who have been impacted by a mitochondrial disease diagnosis. This specialised support service is designed to help you navigate the emotional challenges that come with living with mitochondrial disease.

If you’re looking for reliable information to share with your GP, explore our resources for healthcare professionals. For medicine safety questions, visit our mitochondrial disease drug information page. And if today feels heavy, please get in touch. The Lily Foundation are here to provide practical advice, emotional support and a community that understands – because no one has to face mito alone.

Frequently asked questions

How is mito diagnosed?

Through a combination of clinical assessment, targeted blood and urine tests, imaging, sometimes muscle biopsy, and modern genetic testing. In the UK this is co-ordinated by specialist NHS services.

What tests diagnose mitochondrial disorders?

Commonly lactate and metabolic profiles, MRI, cardiac and hearing assessments, and genetic testing of mitochondrial DNA and nuclear genes. Muscle, skin and liver biopsy may be considered when indicated by clinical, genetic and radiological findings.

How do you test the health of your mitochondria?

There’s no single consumer test. Clinicians assess mitochondrial function indirectly through clinical features, lab markers, imaging and, where appropriate, tissue studies and genetics.

What are the red flags for mitochondrial disease?

Unexplained fatigue and muscle weakness, seizures or stroke-like episodes, developmental delay or regression, hearing or vision loss, and multi-system symptoms occurring together.

What can mimic mitochondrial disease?

Autoimmune and inflammatory diseases, other metabolic disorders, muscular dystrophies, thyroid problems, neuropathies and the effects of certain medications.

What kind of doctor diagnoses mitochondrial dysfunction?

Neurologists, clinical geneticists and metabolic physicians working in both paediatric and adult clinical settings within the NHS, often in a multidisciplinary team. There are also a small number of doctors specialising in mitochondrial medicine who work in the NHS Highly Specialised Service for Rare Mitochondrial Disorders.

Can mitochondrial disease be missed?

Yes. Mitochondrial disease can be missed or misdiagnosed, especially when symptoms are mild, non‑specific or affect only one organ system. Routine tests may appear normal, and symptoms often overlap with more common neurological, metabolic or autoimmune conditions. Specialist assessment is often needed to recognise underlying mitochondrial disease.

It’s also important to understand that mitochondrial disease evolves over time. It’s very unlikely that anyone would be diagnosed with mitochondrial disease when they develop diabetes mellitus alone, but if they become severely hearing impaired a few years later then the correct diagnosis may be more obvious.

Can you have it with normal test results?

Many people with mitochondrial disease have normal routine tests. Specialist investigations are often needed.

Is mitochondrial disease always inherited?

Most mitochondrial diseases are genetic, but inheritance patterns vary. Some are inherited through the mitochondrial DNA (usually maternal), others through nuclear genes following autosomal recessive or dominant patterns. In some cases, a genetic change arises for the first time in an individual with no family history. Read more about understanding inheritance patterns in mitochondrial disease over in our Research Zone.

Can adults be diagnosed later in life?

Yes. Many people are diagnosed in adolescence or adulthood, even if the genetic change has been present since birth. Adult‑onset mitochondrial disease often develops gradually and may initially cause fatigue, muscle weakness or neurological symptoms, which can delay referral for specialist testing and diagnosis.

Experience of diagnosis in mitochondrial disease study

In 2025 The Lily Foundation led a piece of research looking in depth at how patients and families experience the moment of receiving a mitochondrial disease diagnosis.

Through our work funding the Precision Medicine Diagnostics Project, patient engagement work with our community highlighted the need to look more closely at the quality of the diagnostic experience, not just the science behind it.

It’s an aspect of the diagnostic odyssey that remains under-researched, particularly from the patient perspective. While most existing studies focus on caregivers, very few explore patients’ own experiences of receiving a diagnosis.

Read the results