The HADHA gene helps your body break down certain long chain fats to make energy, especially during fasting, sleep, or illness. If the gene does not work properly, cells may struggle to use fat as fuel, which can lead to low blood sugar, low energy, liver or heart problems, and muscle weakness. Some people with HADHA variants also develop nerve symptoms or eye changes over time. Understanding this gene can help you make sense of how your body handles energy under stress.
What is a gene?
Genes are stretches of DNA that carry instructions your cells use to make molecules or control activities in the body. Some genes provide the directions for producing proteins, the parts of cells that do much of the work. Other genes mainly regulate when certain processes happen, where they happen, and how active they are. Together, genes affect how the body develops and works, and they can also influence how you respond to food, stress, or medications. For a deeper look at this topic, you can find more in LearnHub.
Overview
HADHAGene function
What if the gene works
The HADHA gene helps your cells break down long chain fats to make energy. This is especially important during fasting or exercise and in organs that need steady fuel, like the heart, muscles, and liver.
Risk
What if the gene does not work
Variants in the HADHA gene can cause LCHAD or mitochondrial trifunctional protein deficiency, affecting long-chain fat use. This can lead to low blood sugar, liver, heart, muscle, or nerve problems. Milder to more severe variants can affect timing and severity.
Treatment
What does that mean for your treatment
Pathogenic variants in the HADHA gene usually shift treatment toward long-chain fat restriction, avoidance of fasting, and calories from medium-chain triglycerides with essential fatty acid support. During illness or heavy exercise, rapid carbohydrate support and sick-day planning help reduce metabolic stress. Triheptanoin is an established option for some people with long-chain fatty acid oxidation conditions, including HADHA-related disease.
Conditions associated with HADHA
Gene function
What if the gene works
Your body uses the HADHA gene to turn certain fats into usable energy, especially between meals or during longer periods of activity. Inside mitochondria (the energy making parts of cells), it helps process long chain fatty acids step by step. This is a central part of how the HADHA gene helps break down fats for energy.
The HADHA gene helps cells handle long chain fats, which are an important stored fuel. It carries out key early reactions that prepare these fats to release energy.
Inside mitochondria, this gene provides two of the three main enzyme activities in a three step fat processing team. That stepwise work helps cells convert fat into energy in a controlled way.
Many tissues use this pathway when they need a steady energy supply, including the heart and skeletal muscles. It is especially useful during fasting, sleep, or endurance activity, when the body leans more on fat as fuel.
The protein made from the HADHA gene works closely with the protein from the HADHB gene in the same mitochondrial fat processing team. Together, they keep long chain fat breakdown moving from one step to the next.
What is a variant?
A genetic variant is a minor change in a gene’s DNA sequence. These changes are common and are part of normal human diversity, including differences in appearance, metabolism, and the way the body responds to environmental influences. Many do not have any noticeable effect and simply represent natural genetic variation. At times, though, a variant can change how a gene works more significantly and may contribute to, or cause, a genetic condition.
Genetic variants
What if the gene does not work
Variants in the HADHA gene can alter the protein's shape or stability, causing it to break down faster, work less effectively, or fail to link up properly with partner proteins. In practical terms, how HADHA gene variants affect protein function depends on the change: some leave partial activity, while more disruptive variants can reduce activity much more. This functional range can shape whether disease linked to the HADHA gene appears earlier and is more pronounced, or later and more variable.
How variants are linked to conditions
Pathogenic variants in the HADHA gene cause long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency, often called LCHAD deficiency, and can also cause mitochondrial trifunctional protein deficiency. These rare inherited conditions may lead to low blood sugar, liver problems, muscle symptoms, nerve damage, heart involvement, and eye changes. In someone with matching symptoms, finding pathogenic variants in both copies of the HADHA gene can confirm the diagnosis.
A variant is not necessarily a diagnosis
Genetic variants are a routine part of human biology and are common in the general population. Most do not directly affect health and simply reflect natural variation among people. For many genes, having a variant associated with a condition points to a possible link rather than a definitive diagnosis, especially when multiple genes and environmental factors also play a role. In some situations, though, a single well-characterized variant in a specific gene can be enough to confirm a diagnosis.
Are there things that can increase or change my risk?
For HADHA, risk is mainly shaped by genetics rather than lifestyle. People who inherit harmful changes in both copies of the HADHA gene can develop a related energy-processing condition, while family history and whether both biological parents carry a HADHA change affect the chance for a child. In people already living with the condition, long fasting, illness, or heavy exercise can trigger symptoms.
Inheritance of HADHA variants
HADHA-related conditions are inherited in an autosomal recessive pattern. This means a child usually inherits one HADHA gene variant from each parent, and both parents are typically healthy carriers. When both parents carry a variant in the HADHA gene, each pregnancy has a 25% chance of being affected, a 50% chance of resulting in a carrier child, and a 25% chance of inheriting neither variant. In practical terms, the HADHA inheritance pattern affects sons and daughters equally.
What does my HADHA result mean for my family?
For HADHA, a result linked to disease usually means the condition runs in a recessive pattern in families. Parents are often healthy carriers, and brothers or sisters may also be affected or be carriers even if they feel well. Other close relatives may also carry the same gene change, so the result can matter for family planning and for understanding risks in the wider family.
Genetic information
Genetic testing
How you find out about variants
Genetic testing for HADHA variants uses a blood sample, saliva, or sometimes a cheek swab. A lab reads the DNA in the HADHA gene and compares it with the usual sequence to find changes that may help explain symptoms or show whether someone is a carrier.
When should I consider getting a genetic test?
Testing for HADHA may be considered if a baby or child has a rare problem using fats for energy, with low blood sugar, liver trouble, heart weakness, or severe symptoms after fasting. It can also help when this condition runs in the family or after a serious pregnancy-related liver problem.
A genetic result is only one part of your health story
A genetic result can provide useful insight, but how much it explains varies based on the condition and the type of variant involved. Many factors, including lifestyle, environment, age, and medical history, shape how the body functions over time. For some conditions, especially those influenced by many genes, genetic information offers context rather than certainty and is best understood alongside other parts of care. In other situations, a genetic result may offer a clear answer. In areas such as medication response, genetic results can help put individual experiences into context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how people respond to medicines. Small differences in genes can change how the body breaks down a drug, moves it through the body, or responds to it at its target. This helps explain why the same medication may work well for one person, seem less effective for another, or cause more side effects in someone else. These differences are common and are one of several factors, along with age, other health conditions, and other medicines, that can shape treatment response.
What is Pharmacogenetics?
Pharmacogenetics is the study of how differences in genes affect the way people respond to medications. It examines links between genes and drugs to help explain why the same treatment may work differently from one person to another. For many medicines, genes can influence how strongly a drug works or how the body handles it. This information can support more informed, more personalized treatment decisions. You can read more about this topic in the LearnHub.
Drugs influenced by the HADHA gene
When should I seek medical advice?
There isn't yet a broadly confirmed role for this gene in guiding medication choices, so questions about side effects, new symptoms, or how a treatment is working are best discussed with your doctor.