Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a type of genetic disorder that chiefly inhibits the body from breaking down certain fats and converting them into energy, particularly during periods without food (fasting). Due to this, the blood sugar levels can drop drastically causing hypoglycemia. This deficiency syndrome is mainly present from birth and is a lifelong condition. If this condition is left untreated for a long time, it can lead to seizures, breathing difficulties, coma and other serious health problems.
Checking blood sugar for MCAD Deficient boy


In a healthy individual, the ACADM gene tells your body to make medium-chain acyl-CoA dehydrogenase, that helps in processing food. There is a specific enzyme 'medium-chain acyl-CoA dehydrogenase' that mainly targets a group of fat called medium-chain fatty acids to convert it into a substance that the body can use (metabolize) as energy. When there is insufficient MCAD enzyme in the body, the medium chain fatty acids can't be broken down and converted into energy. This results in hypoglycemia and low energy levels. Additionally, fatty acids can build up in the body tissues and cause damage to the liver and brain.

MCAD deficiency is genetic in nature and inherited from both the parents. If both parents are carriers of the mutated copy of the ACADM gene, i.e., each has one abnormal gene and no characteristic symptoms of the condition (autosomal recessive), the child still inherits two copies of the abnormal gene and gets affected with the condition. But if you inherit only one mutated copy the ACADM gene, you won't develop MCAD deficiency, but you become a carrier and can pass the abnormal gene to your children later in life. But then again, the child wouldn't develop the condition unless they inherit another affected gene from the other parent.


The characteristic symptoms, of this inherited disorder usually appears in babies and young children. In very rare cases, MCAD deficiency gets unnoticed till adulthood. The typical signs and symptoms include:

  • Vomiting
  • Lack of energy
  • Weakness
  • Being overly sleepy (somnolent)
  • Trouble while breathing or fast breathing
  • Low blood sugar (hypoglycemia)
  • Liver abnormalities (enlargement, high liver enzymes)
  • Seizures

Hypoglycemia can often be triggered by:

  • Going too long without eating or by fasting
  • Not eating enough complex carbohydrates
  • Viral infections and other illnesses
  • Vomiting
  • Diarrhea
  • Recurrent fever
  • Increased exercise
  • Significant stress
  • Vaccinations


If the hypoglycemia caused by MCAD deficiency is left untreated for a long time, it can lead to:

  • Breathing problems
  • Liver problems
  • Seizures
  • Brain damage
  • Coma
  • Sudden death

Diagnosis And Treatment

On noticing the above-mentioned signs and symptoms in your child or yourself, do consult a doctor at the earliest. The doctor usually does a thorough physical check-up and conducts a few diagnostics   In case of a newborn, the doctor will generally conduct newborn screening followed by genetic testing.

In case, the result for newborn screening comes abnormal, the doctor may proceed for additional testing.

In genetic testing, the abnormal gene that causes MCAD deficiency is revealed. Depending on the type of test, a sample of blood, urine, skin or other tissue is collected from the affected baby and sent to a lab for analysis. For further information or to identify the presence of the mutated ACADM gene, the doctor may also recommend testing family members (specially the parents) for the recessive gene.

Other tests to thoroughly access the condition includes:

Blood tests to check glucose, ammonia, and other levels

Urine tests to rule out other conditions that cause low blood sugar


Although this deficiency syndrome doesnot have an absolute cure, but identifying it at a young age helps to subdue the symptoms and manage it effectively. In case of newborn, if the condition is screened right at birth, before the onset of the symptoms, the MCAD deficiency symptoms are well managed through diet and lifestyle.

The primary goal for MCAD deficiency is to manage and prevent problems caused by hypoglycemia from occurring. In the case of infants with MCAD deficiency, the feedings with breast milk or formula milk require to be frequent and with adequate calories from complex carbohydrates to maintain blood sugar and avoid hypoglycemia. In the case of children and adults, the eating schedule should be regular and the meals would also require adequate complex carbohydrates. It is necessary to consult with the health care team, including a dietitian, to develop a treatment plan custom-made to fit your child's or your metabolic needs.

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Dietary requirements for MCAD deficiency include:

  • Scheduling frequent meals throughout the day.
  • Eating a high carbohydrate-rich diet.
  • Tailoring a heart-healthy diet (less fat) for the child.
  • Intake of prescribed carnitine supplements to assist fat to energy conversion.

In the case of adults suffering from MCAD deficiency, the doctor usually forbids the patient to consume excessive fats as it can cause severe symptoms (metabolic crisis). If this occurs, taking a glucose supplement or eating foods high in sugar helps manage the side effects of the condition.

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Lifestyle Modifications To Manage MCAD

It is vital for parents and family members to understand the condition for the ongoing care and prevention of hypoglycemia episodes and complications.

Prevention tips mainly include:

  • Evade from fasting
  • Acknowledge the warning signs of hypoglycemia and treat it on an urgent basis
  • Consume complex carbohydrates before extra activity or exercise
  • Increase intake of calories with extra complex carbohydrates during illness, stress or increased activity
  • Always carry a source of simple carbohydrates to treat hypoglycemia
  • Always carry complex carbohydrate snacks along with yourself