concerned looking rescue Cavalier King Charles Spaniel
Navigating the Initial Milestones with Your Rescue Cavalier
26th August 2023
Ruby Cavalier Arlo with MCADD

Reading this could save your dog’s life.

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD), a fatty acid oxidation disorder, is an inherited disease affecting the Cavalier King Charles Spaniel breed.

What is MCADD?

This condition prevents the normal use of fat as an alternative energy source during fasting or increased metabolic demands.

Affected animals cannot burn fat for energy when their bodies run out of glucose, and as a result, they may be affected by low blood sugar, altered central nervous system function, coma, or sudden death. With an early diagnosis, MCADD can be managed successfully by diet.

Owners are being advised not to feed MCT oils unless their dog has been tested clear for the ACADM mutation causing the MCAD deficiency.

While it is a well-documented condition in humans, there’s less extensive literature and research about MCADD in dogs.

Nonetheless, here’s some basic information on what you might expect if a dog has a metabolic disorder. This is new to us, so there may be further clinical signs found as more cases are diagnosed.

  1. Clinical Signs:
    • Hypoglycemia: Due to an inability to properly utilise fats for energy, affected dogs might experience low blood sugar.
    • Lethargy: Dogs might show signs of weakness or lethargy due to energy depletion.
    • Muscle Weakness: Impaired fatty acid metabolism could lead to muscle weakness or pain.
    • Hypoketotic Hypoglycemia: It is characterised by low levels of ketones and blood sugar, resulting in weakness, lethargy, and other symptoms.
  2. Diagnosis:
    • Diagnosis in dogs would require a DNA test to confirm the presence of mutations in the relevant gene. (Details below)
  3. Management:
    • Managing MCADD in dogs, much like in humans, would potentially involve dietary modifications to avoid fasting and ensure a steady supply of glucose, along with regular monitoring and veterinary check-ups.
    • Cavaliers should abstain from foods with coconut oil, palm kernel oil, or any other medium-chain triglycerides (MCTs) unless they have been tested and determined to be clear or merely a carrier of the mutated gene inducing MCADD.
  4. Prognosis:
    • If identified and managed properly, dogs with MCADD can often lead relatively normal lives, though they might require special care, dietary restrictions, and regular monitoring to avoid metabolic crises.

If you suspect a pet has a metabolic disorder like MCADD or is showing unusual clinical signs such as frequent lethargy, hypoglycemia, or muscle weakness, it is crucial to consult with a veterinarian. This is a newly found condition, so many vets may not be fully aware of it, although, with some research, they should be able to give you more information.

How many Cavaliers are affected?

It is early days, but at the moment (September 2023) it is approximately 5-9% of the Cavaliers tested so far are affected.

How do I test my Cavalier for MCADD?

If your Cavalier has ever had a seizure or lethargy with an unknown cause, even if it’s just a one-off, you should get the MCADD DNA test. It is inexpensive and could save your dogs life. Available at and

There is a fantastic Facebook group for further information – MCADD in the Cavalier King Charles Spaniel

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