Draft — awaiting clinical review

MCAD Deficiency (MCADD)

In plain words: The body has trouble turning certain fats into energy. Going too long without food can become dangerous, so regular meals and an illness plan matter.

Your genetics may influence your health, but they do not determine your worth. Understanding your body creates opportunities for informed care—not blame.

Designed to Heal provides general educational information and personal wellness tools. It does not diagnose genetic conditions, interpret genetic tests, or replace qualified medical care. Genetic disorders may require specialized diets, medication, monitoring, or other medical treatments. Consult a qualified healthcare professional before changing your treatment, nutrition, or exercise plan.

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We do not diagnose, interpret genetic tests or calculate risk. For testing or family-planning questions, ask your clinician about a certified genetic counselor.

1. Overview

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) affects how the body uses fat for energy, especially when glucose runs low. Many babies are identified through newborn screening.

2. Genetic cause and inheritance

Caused by changes in the ACADM gene. It is autosomal recessive.

3. Symptoms and complications

Episodes often triggered by fasting or illness
Vomiting, low energy, extreme sleepiness
Low blood sugar
Without quick treatment, episodes can lead to seizures, breathing problems or be life-threatening

4. How clinicians diagnose it

Usually found by newborn screening, then confirmed with blood and urine tests and genetic testing by a metabolic specialist.

5. Established medical treatment

Avoiding long periods without food, with timing set by your metabolic team
An emergency letter and sick-day plan, often including IV glucose at the hospital
Some people may be advised to take a supplement such as carnitine by their specialist

6. Nutrition considerations

Fasting may be dangerous with MCADD. Intermittent fasting, skipped meals, very low-carbohydrate or 'cleanse' diets are not appropriate unless your metabolic team says otherwise.

Nutrition, movement and other supportive practices may support overall health, but they cannot change the inherited genetic variant.

7. Activity considerations

Activity is usually fine with good fueling. Ask your team how to eat before, during and after long exercise.

8. Safety precautions

Do not fast — follow the maximum time between meals your team gives you
If you can't eat or keep food down during illness, seek care promptly and show your emergency letter
Tell surgeons and anesthesiologists about MCADD before any procedure that requires fasting

9. Questions to ask your clinician

What is the longest I can safely go without eating?
What should I do when I'm sick and can't eat?
Can I have an emergency letter for the ER?

10. References

MedlinePlus Genetics — Medium-chain acyl-CoA dehydrogenase deficiency

Last updated October 8, 2026