Medical Conditions

Carnitine Deficiency in Babies

Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist

Content reviewed against published NIH, NIH, ACMG guidelines

Editorial policy

Last reviewed: July 2026

If your baby has been diagnosed with or you suspect carnitine deficiency in babies, here is what the evidence says.

The short answer

Key takeaways

Carnitine deficiency occurs when the body cannot properly transport long-chain fatty acids into mitochondria for energy production. Primary carnitine deficiency (carnitine transporter defect) affects about 1 in 40,000 to 120,000 newborns and is caused by mutations in the SLC22A5 gene. It can cause muscle weakness, heart problems (cardiomyopathy), and life-threatening hypoglycemia, especially during fasting or illness. With early detection through newborn screening and lifelong carnitine supplementation, most children develop normally.
Usually normal when: Your baby was identified through newborn screening, is on carnitine supplementation, and is developing normally
Call your doctor if: Your baby is excessively sleepy, vomiting, refusing to feed, or having rapid breathing during an illness — this may indicate metabolic crisis requiring emergency treatment
Varies by age — see the age-by-age breakdown below

“Fever itself is not an illness — rather, it is a sign or symptom that the body is fighting an infection. Fever stimulates certain defenses, such as the white blood cells, which attack and destroy invading bacteria.”

— Fever and Your Child, American Academy of Pediatrics (AAP)

This is one of the most common questions parents ask. Searching for answers means you care.

What Parents Should Know

According to NIH, ACMG guidelines, carnitine deficiency occurs when the body cannot properly transport long-chain fatty acids into mitochondria for energy production. Primary carnitine deficiency (carnitine transporter defect) affects about 1 in 40,000 to 120,000 newborns and is caused by mutations in the SLC22A5 gene. It can cause muscle weakness, heart problems (cardiomyopathy), and life-threatening hypoglycemia, especially during fasting or illness. With early detection through newborn screening and lifelong carnitine supplementation, most children develop normally. At 0-3 months, primary carnitine deficiency is often detected through newborn screening, which measures free carnitine levels in dried blood spots. Affected newborns may appear healthy at birth because they have been receiving carnitine from the mother during pregnancy. Some infants present with hypoglycemia, lethargy, or poor feeding in the newborn period, particularly during periods of fasting or illness. If newborn screening flags low carnitine, confirmatory testing with plasma carnitine levels and genetic testing is performed promptly. Carnitine supplementation is typically started immediately upon diagnosis. It is generally considered normal when your baby was identified through newborn screening, is on carnitine supplementation, and is developing normally. However, you should contact your pediatrician promptly if your baby is excessively sleepy, vomiting, refusing to feed, or having rapid breathing during an illness — this may indicate metabolic crisis requiring emergency treatment.

Sources: [1], [2], [3]

Normal vs. Concerning

Usually Normal

Worth Discussing

Your baby was identified through newborn screening, is on carnitine supplementation, and is developing normally

Your baby is excessively sleepy, vomiting, refusing to feed, or having rapid breathing during an illness — this may indicate metabolic crisis requiring emergency treatment

Your baby's carnitine levels are within the therapeutic range on regular follow-up blood work

Your baby has signs of heart failure — rapid breathing, sweating with feeding, poor color, or swelling — seek emergency care immediately

Your baby's echocardiogram shows normal heart function on treatment

Your baby has had a seizure or episode of unresponsiveness, which may indicate severe hypoglycemia

Your baby is feeding well, gaining weight appropriately, and meeting developmental milestones

Your baby's newborn screening showed low free carnitine and you are awaiting confirmatory testing

When to Seek Immediate Care

Your baby is excessively sleepy, vomiting, refusing to feed, or having rapid breathing during an illness — this may indicate metabolic crisis requiring emergency treatment
Your baby has signs of heart failure — rapid breathing, sweating with feeding, poor color, or swelling — seek emergency care immediately
Your baby has had a seizure or episode of unresponsiveness, which may indicate severe hypoglycemia

By Age

What to expect by age

0-3 months

Primary carnitine deficiency is often detected through newborn screening, which measures free carnitine levels in dried blood spots. Affected newborns may appear healthy at birth because they have been receiving carnitine from the mother during pregnancy. Some infants present with hypoglycemia, lethargy, or poor feeding in the newborn period, particularly during periods of fasting or illness. If newborn screening flags low carnitine, confirmatory testing with plasma carnitine levels and genetic testing is performed promptly. Carnitine supplementation is typically started immediately upon diagnosis.

1-6 months

Without treatment, carnitine levels gradually decrease as maternal carnitine stores are depleted. Symptoms can include poor feeding, failure to thrive, muscle weakness (hypotonia), and lethargy. Some infants develop cardiomyopathy (enlarged, weakened heart), which can progress rapidly. Liver dysfunction may also occur. With early carnitine supplementation (typically oral L-carnitine), these complications can be prevented or reversed. Echocardiography is used to monitor heart function.

6-12 months

Babies on carnitine supplementation typically develop normally. The primary risk during this period is metabolic decompensation during illness, when energy demands increase and the baby may not eat well. Parents should have a sick-day management plan from their metabolic specialist. Signs of metabolic crisis include excessive sleepiness, vomiting, rapid breathing, and refusal to feed. These require urgent medical attention. Regular monitoring of carnitine levels and heart function continues.

1-3 years

Children with well-managed primary carnitine deficiency on consistent L-carnitine supplementation generally achieve normal developmental milestones. The medication is lifelong but well tolerated. Sick-day protocols remain important, as toddlers are prone to viral illnesses with reduced oral intake. Fasting should be avoided. Some children may need dose adjustments as they grow. Cardiac function typically normalizes with treatment, and long-term prognosis is excellent with adherence to supplementation.

What to Tell Your Pediatrician

Describe when you first noticed carnitine deficiency in babies and how it has changed over time.
Note your baby's current age and which age-specific patterns you are seeing.
Mention if your baby's newborn screening showed low free carnitine and you are awaiting confirmatory testing.
Mention if your baby on carnitine supplementation has persistent muscle weakness or poor weight gain.
Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
Bring a list of any questions or observations you want to discuss at the appointment.

What Should You Do?

When to take action

Probably normal when...

Your baby was identified through newborn screening, is on carnitine supplementation, and is developing normally
Your baby's carnitine levels are within the therapeutic range on regular follow-up blood work
Your baby's echocardiogram shows normal heart function on treatment
Your baby is feeding well, gaining weight appropriately, and meeting developmental milestones

Mention at your next visit when...

Your baby's newborn screening showed low free carnitine and you are awaiting confirmatory testing
Your baby on carnitine supplementation has persistent muscle weakness or poor weight gain
Your baby with carnitine deficiency is having difficulty tolerating the oral supplement
You are planning travel or changes in routine and need guidance on sick-day management

Act now when...

Your baby is excessively sleepy, vomiting, refusing to feed, or having rapid breathing during an illness — this may indicate metabolic crisis requiring emergency treatment
Your baby has signs of heart failure — rapid breathing, sweating with feeding, poor color, or swelling — seek emergency care immediately
Your baby has had a seizure or episode of unresponsiveness, which may indicate severe hypoglycemia

What You Can Do at Home

Keep track of when you notice carnitine deficiency in babies — noting the time of day, duration, and any triggers can help your pediatrician.
Remember that your baby was identified through newborn screening, is on carnitine supplementation, and is developing normally — this is generally within the range of normal.
At 0-3 months, focus on observation rather than intervention unless your pediatrician advises otherwise.
Follow any care instructions from your pediatrician. Keep a written log of symptoms to bring to appointments.
While monitoring at home, seek immediate care if your baby is excessively sleepy, vomiting, refusing to feed, or having rapid breathing during an illness — this may indicate metabolic crisis requiring emergency treatment.

Abnormal Newborn Screening Results

An abnormal or positive newborn screening result means that further testing is needed, not that your baby definitely has a condition. Most positive screens turn out to be false positives after confirmatory testing. Newborn screening tests are intentionally sensitive to avoid missing any affected babies, so follow-up testing is essential to determine whether the result is a true positive.

Cardiomyopathy in Babies

Cardiomyopathy is a disease of the heart muscle that affects how well the heart can pump blood. In babies, the main types are dilated cardiomyopathy (the heart becomes enlarged and weakened), hypertrophic cardiomyopathy (the heart muscle becomes abnormally thick), and restrictive cardiomyopathy (the heart muscle becomes stiff). Signs in infants include rapid breathing, poor feeding, excessive sweating, poor weight gain, and a fast heartbeat. Cardiomyopathy in babies can be inherited, caused by infection, or have no identifiable cause. Early diagnosis and treatment by a pediatric cardiologist are essential.

Milestone

Month-by-Month Development

Detailed monthly development guides from birth through 24 months.

Guide

When to Call the Doctor

General guide on when to call the pediatrician, visit urgent care, or go to the ER.

Frequently asked questions

Is carnitine deficiency in babies normal?

When should I call the doctor about carnitine deficiency in babies?

Your baby is excessively sleepy, vomiting, refusing to feed, or having rapid breathing during an illness — this may indicate metabolic crisis requiring emergency treatment Your baby has signs of heart failure — rapid breathing, sweating with feeding, poor color, or swelling — seek emergency care immediately Your baby has had a seizure or episode of unresponsiveness, which may indicate severe hypoglycemia

When is carnitine deficiency in babies normal?

Your baby was identified through newborn screening, is on carnitine supplementation, and is developing normally Your baby's carnitine levels are within the therapeutic range on regular follow-up blood work Your baby's echocardiogram shows normal heart function on treatment

What causes carnitine deficiency in babies?

Carnitine deficiency occurs when the body cannot properly transport long-chain fatty acids into mitochondria for energy production. Primary carnitine deficiency (carnitine transporter defect) affects about 1 in 40,000 to 120,000 newborns and is caused by mutations in the SLC22A5 gene. It can cause muscle weakness, heart problems (cardiomyopathy), and life-threatening hypoglycemia, especially during fasting or illness. With early detection through newborn screening and lifelong carnitine supplementation, most children develop normally. Common explanations include: Your baby was identified through newborn screening, is on carnitine supplementation, and is developing normally. Your baby's carnitine levels are within the therapeutic range on regular follow-up blood work.

What should I mention to my pediatrician about carnitine deficiency in babies?

You should mention carnitine deficiency in babies at your next visit if: Your baby's newborn screening showed low free carnitine and you are awaiting confirmatory testing. Your baby on carnitine supplementation has persistent muscle weakness or poor weight gain. Your baby with carnitine deficiency is having difficulty tolerating the oral supplement.

Is carnitine deficiency in babies normal at 0-3 months?

Is carnitine deficiency in babies normal at 1-6 months?

Should I go to the ER for carnitine deficiency in babies?

Seek emergency care if your baby is excessively sleepy, vomiting, refusing to feed, or having rapid breathing during an illness — this may indicate metabolic crisis requiring emergency treatment, or if your baby has signs of heart failure — rapid breathing, sweating with feeding, poor color, or swelling — seek emergency care immediately. When in doubt, call your pediatrician's after-hours line for guidance.

Does carnitine deficiency in babies go away on its own?

In many cases, carnitine deficiency in babies resolves on its own, especially when your baby was identified through newborn screening, is on carnitine supplementation, and is developing normally. By 1-3 years, children with well-managed primary carnitine deficiency on consistent L-carnitine supplementation generally achieve normal developmental milestones. The medication is lifelong but well tolerated. Sick-day protocols remain important, as toddlers are prone to viral illnesses with reduced oral intake. Fasting should be avoided. Some children may need dose adjustments as they grow. Cardiac function typically normalizes with treatment, and long-term prognosis is excellent with adherence to supplementation.

NIH NIH ACMG

References

[1]National Library of Medicine. Systemic Primary Carnitine Deficiency. GeneReviews, 2023. NIH
[2]National Library of Medicine. Primary Carnitine Deficiency. MedlinePlus Genetics, 2023. NIH
[3]American College of Medical Genetics and Genomics. Newborn Screening ACT Sheet: Decreased Free Carnitine. ACMG, 2023. ACMG

Doctor Visit Checklist

Bring this checklist to your next pediatrician visit to discuss Carnitine Deficiency in Babies.

Things to mention

Describe when you first noticed carnitine deficiency in babies and how it has changed over time.
Note your baby's current age and which age-specific patterns you are seeing.
Mention if your baby's newborn screening showed low free carnitine and you are awaiting confirmatory testing.
Mention if your baby on carnitine supplementation has persistent muscle weakness or poor weight gain.
Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
Bring a list of any questions or observations you want to discuss at the appointment.

Observations to share

Your baby's newborn screening showed low free carnitine and you are awaiting confirmatory testing
Your baby on carnitine supplementation has persistent muscle weakness or poor weight gain
Your baby with carnitine deficiency is having difficulty tolerating the oral supplement

Urgent signs to report immediately

Your baby is excessively sleepy, vomiting, refusing to feed, or having rapid breathing during an illness — this may indicate metabolic crisis requiring emergency treatment
Your baby has signs of heart failure — rapid breathing, sweating with feeding, poor color, or swelling — seek emergency care immediately
Your baby has had a seizure or episode of unresponsiveness, which may indicate severe hypoglycemia

My notes

From ismybabyalright.com — free, evidence-based baby health guides

All content follows our editorial policy and is reviewed against published clinical guidelines.

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Bottom line

Most cases of carnitine deficiency in babies are normal. Talk to your pediatrician if your baby is excessively sleepy, vomiting, refusing to feed, or having rapid breathing during an illness — this may indicate metabolic crisis requiring emergency treatment.

Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.

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Abnormal Newborn Screening Results

Cardiomyopathy in Babies

My Baby's Head Shape Looks Abnormal

Many babies develop temporary head shape irregularities that are completely normal. A cone-shaped head from vaginal delivery reshapes within days. Mild positional flattening (plagiocephaly) from sleeping on the back is very common and usually improves with repositioning and tummy time. However, head shape changes involving ridges, a persistently bulging fontanelle, or rapid head growth changes should be evaluated to rule out craniosynostosis.

Achondroplasia (Dwarfism) in Babies

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Adenoid Hypertrophy and Breathing

Adenoids are lymphoid tissue located behind the nose that help fight infection in young children. When adenoids become enlarged (adenoid hypertrophy), they can block the nasal airway, causing chronic mouth breathing, snoring, nasal speech, and sleep-disordered breathing. Enlarged adenoids are most common between ages 2-7 and are a leading cause of obstructive sleep apnea in young children. Treatment ranges from watchful waiting and nasal steroids to surgical removal (adenoidectomy) if breathing or sleep is significantly affected.

Adrenoleukodystrophy (ALD) in Babies

X-linked adrenoleukodystrophy (X-ALD) is a genetic disorder affecting about 1 in 17,000 newborns, caused by mutations in the ABCD1 gene on the X chromosome. It primarily affects boys and impairs the breakdown of very long-chain fatty acids (VLCFAs), which accumulate and damage the myelin sheath in the brain and the adrenal glands. The most severe form, cerebral ALD, typically affects boys between ages 4-10 with rapid neurological decline. Newborn screening now enables early detection, and hematopoietic stem cell transplant or gene therapy performed before significant brain involvement can be life-saving.