On 9 May 2014, the UK National Screening Committee (UK NSC) announced its recommendation to screen every newborn baby in the UK for four further genetic disorders as part of its NHS Newborn Blood Spot Screening programme, including isovaleric acidemia.

In most regions, galactosemia is diagnosed as a result of newborn screening, most commonly by determining the concentration of galactose in a dried blood spot. Some regions will perform a second-tier test of GALT enzyme activity on samples with elevated galactose, while others perform both GALT and galactose measurements. While awaiting confirmatory testing for classic galactosemia, the infant is typically fed a soy-based formula, as human and cow milk contains galactose as a component of lactose. Confirmatory testing would include measurement of enzyme activity in red blood cells, determination of Gal-1-P levels in the blood, and mutation testing. The differential diagnosis for elevated galactose concentrations in blood on a newborn screening result can include other disorders of galactose metabolism, including galactokinase deficiency and galactose epimerase deficiency. Enzyme assays are commonly done using fluorometric detection or older radioactively labeled substrates.

Most individuals with SBCADD are identified through newborn screening, where they present with an elevation of a five carbon acylcarnitine species. Confirmatory testing includes plasma and urine analysis to identify the carnitine and glycine conjugates of 2-methylbutyryl-CoA.

Dozens of congenital metabolic diseases are now detectable by newborn screening tests, especially the expanded testing using mass spectrometry. This is an increasingly common way for the diagnosis to be made and sometimes results in earlier treatment and a better outcome. There is a revolutionary Gas chromatography–mass spectrometry-based technology with an integrated analytics system, which has now made it possible to test a newborn for over 100 mm genetic metabolic disorders.

Because of the multiplicity of conditions, many different diagnostic tests are used for screening. An abnormal result is often followed by a subsequent "definitive test" to confirm the suspected diagnosis.

Common screening tests used in the last sixty years:

- Ferric chloride test (turned colors in reaction to various abnormal metabolites in urine)

- Ninhydrin paper chromatography (detected abnormal amino acid patterns)

- Guthrie bacterial inhibition assay (detected a few amino acids in excessive amounts in blood) The dried blood spot can be used for multianalyte testing using Tandem Mass Spectrometry (MS/MS). This given an indication for a disorder. The same has to be further confirmed by enzyme assays, IEX-Ninhydrin, GC/MS or DNA Testing.

- Quantitative measurement of amino acids in plasma and urine

- IEX-Ninhydrin post column derivitization liquid ion-exchange chromatography (detected abnormal amino acid patterns and quantitative analysis)

- Urine organic acid analysis by gas chromatography–mass spectrometry

- Plasma acylcarnitines analysis by mass spectrometry

- Urine purines and pyrimidines analysis by gas chromatography-mass spectrometry

Specific diagnostic tests (or focused screening for a small set of disorders):

- Tissue biopsy or necropsy: liver, muscle, brain, bone marrow

- Skin biopsy and fibroblast cultivation for specific enzyme testing

- Specific DNA testing

A 2015 review reported that even with all these diagnostic tests, there are cases when "biochemical testing, gene sequencing, and enzymatic testing can neither confirm nor rule out an IEM, resulting in the need to rely on the patient's clinical course."

The urine of newborns can be screened for isovaleric acidemia using mass spectrometry, allowing for early diagnosis. Elevations of isovalerylglycine in urine and of isovalerylcarnitine in plasma are found.

Infant mortality is high for patients diagnosed with early onset; mortality can occur within less than 2 months, while children diagnosed with late-onset syndrome seem to have higher rates of survival. Patients suffering from a complete lesion of mut0 have not only the poorest outcome of those suffering from methylaonyl-CoA mutase deficiency, but also of all individuals suffering from any form of methylmalonic acidemia.

Biotinidase deficiency can be found by genetic testing. This is often done at birth as part of newborn screening in several states throughout the United States. Results are found through testing a small amount of blood gathered through a heel prick of the infant. As not all states require that this test be done, it is often skipped in those where such testing is not required. Biotinidase deficiency can also be found by sequencing the "BTD" gene, particularly in those with a family history or known familial gene mutation.

There are no methods for preventing the manifestation of the pathology of MSUD in infants with two defective copies of the BCKD gene. However, genetic counselors may consult with couples to screen for the disease via DNA testing. DNA testing is also available to identify the disease in an unborn child in the womb.

Diagnosis of Fatty-acid metabolism disorder requires extensive lab testing.

Normally, in cases of hypoglycaemia, triglycerides and fatty acids are metabolised to provide glucose/energy. However, in this process, ketones are also produced and ketotic hypoglycaemia is expected. However, in cases where fatty acid metabolism is impaired, a non-ketotic hypoglycaemia may be the result, due to a break in the metabolic pathways for fatty-acid metabolism.

On 9 May 2014, the UK National Screening Committee (UK NSC) announced its recommendation to screen every newborn baby in the UK for four further genetic disorders as part of its NHS Newborn Blood Spot Screening programme, including maple syrup urine disease.

Newborn screening for maple syrup urine disease involves analyzing the blood of 1–2 day-old newborns through tandem mass spectrometry. The blood concentration of leucine and isoleucine is measured relative to other amino acids to determine if the newborn has a high level of branched-chain amino acids. Once the newborn is 2–3 days old the blood concentration of branched-chain amino acids like leucine is greater than 1000 µmol/L and alternative screening methods are used. Instead, the newborn’s urine is analyzed for levels of branched-chain alpha-hydroxyacids and alpha-ketoacids.

One of, if not the most common form of organic acidemia, methylmalonic acidemia is not apparent at birth as symptoms usually do not present themselves until proteins are added to the infant's diet. Because of this, symptoms typically manifest anytime within the first year of life. Due to the severity and rapidity in which this disorder can cause complications when left undiagnosed, screening for methylmalonic acidemia is often included in the newborn screening exam.

Because of the inability to properly break down amino acids completely, the byproduct of protein digestion, the compound methylmalonic acid, is found in a disproportionate concentration in the blood and urine of those afflicted. These abnormal levels are used as the main diagnostic criteria for diagnosing the disorder. This disorder is typically determined through the use of a urine analysis or blood panel. The presence of methylmalonic acidemia can also be suspected through the use of a CT or MRI scan or ammonia test, however these tests are by no means specific and require clinical and metabolic/correlation. Elevated levels of ammonia, glycine, and ketone bodies may also be present in the blood and urine.

Metabolic disorder screening can be done in newborns via the following methods:

- Blood test

- Skin test

- Hearing test

Histidenemia is characterized by increased levels of histidine, histamine and imidazole in blood, urine and cerebrospinal fluid. This also results in decreased levels of the metabolite urocanic acid in blood, urine, and skin cells. In Japan, neonatal screening was previously performed on infants within 1 month of birth; infants demonstrating a blood histidine level of 6 mg/dl or more underwent careful testing as suspected histidinemia cases. A typical characteristic of histidinemia is an increase in the blood histidine levels from normal levels (70-120 μM) to an elevated level (290-1420 μM). Further testing includes: observing histidine as well as imidazolepyruvic acid metabolites in the urine. However, neonatal urine testing has been discontinued in most places, with the exception of Quebec.

Based on the results of worldwide screening of biotinidase deficiency in 1991, the incidence of the disorder is:

5 in 137,401 for profound biotinidase deficiency

- One in 109,921 for partial biotinidase deficiency

- One in 61,067 for the combined incidence of profound and partial biotinidase deficiency

- Carrier frequency in the general population is approximately one in 120.

Individuals presenting with Type III galactosemia must consume a lactose- and galactose-restricted diet devoid of dairy products and mucilaginous plants. Dietary restriction is the only current treatment available for GALE deficiency. As glycoprotein and glycolipid metabolism generate endogenous galactose, however, Type III galactosemia may not be resolved solely through dietary restriction.

Methylmalonic acidemia has varying diagnoses, treatment requirements and prognoses, which are determined by the specific genetic mutation causing the inherited form of the disorder. The following are the known genotypes responsible for methylmalonic acidemia:

The mut type can further be divided in mut0 and mut- subtypes, with mut0 characterized by a complete lack of methylmalonyl CoA mutase and more severe symptoms and mut- characterized by a decreased amount of mutase activity.

Mut-, cblB, and cblA versions of methylmalonic acidemia have been found to be cobalamin responsive. Mut0 is a nonresponsive variant.

Several tests can be done to discover the dysfunction of methylmalonyl-CoA mutase. Ammonia test, blood count, CT scan, MRI scan, electrolyte levels, genetic testing, methylmalonic acid blood test, and blood plasma amino acid tests all can be conducted to determine deficiency.

There is no treatment for complete lesion of the mut0 gene, though several treatments can help those with slight genetic dysfunction. Liver and kidney transplants, and a low-protein diet all help regulate the effects of the diseases.

In the middle of the 20th century the principal treatment for some of the amino acid disorders was restriction of dietary protein and all other care was simply management of complications. In the past twenty years, enzyme replacement, gene therapy, and organ transplantation have become available and beneficial for many previously untreatable disorders. Some of the more common or promising therapies are listed:

It has been suggested that a possible method of treatment for histidinemia is through the adoption of a diet that is low in histidine intake. However, the requirement for such dietary restrictions is typically unnecessary for 99% of all cases of histidinemia.

Screening for elevated galactose levels may detect GALE deficiency or dysfunction in infants, and mutation studies for GALE are clinically available.

Carnitor - an L-carnitine supplement that has shown to improve the body's metabolism in individuals with low L-carnitine levels. It is only useful for Specific fatty-acid metabolism disease.

Treatment or management of organic acidemias vary; eg see methylmalonic acidemia, propionic acidemia, isovaleric acidemia, and maple syrup urine disease.

As of 1984 there were no effective treatments for all of the conditions, though treatment for some included a limited protein/high carbohydrate diet, intravenous fluids, amino acid substitution, vitamin supplementation, carnitine, induced anabolism, and in some cases, tube-feeding.

As of 1993 ketothiolase deficiency and other OAs were managed by trying to restore biochemical and physiologic homeostasis; common therapies included restricting diet to avoid the precursor amino acids and use of compounds to either dispose of toxic metabolites or increase enzyme activity.

There is no cure for GALT deficiency, in the most severely affected patients, treatment involves a galactose free diet for life. Early identification and implementation of a modified diet greatly improves the outcome for patients. The extent of residual GALT enzyme activity determines the degree of dietary restriction. Patients with higher levels of residual enzyme activity can typically tolerate higher levels of galactose in their diets. As patients get older, dietary restriction is often relaxed. With the increased identification of patients and their improving outcomes, the management of patients with galactosemia in adulthood is still being understood.

After diagnosis, patients are often supplemented with calcium and vitamin D3. Long-term manifestations of the disease including ovarian failure in females, ataxia. and growth delays are not fully understood. Routine monitoring of patients with GALT deficiency includes determining metabolite levels (galactose 1-phosphate in red blood cells and galactitol in urine) to measure the effectiveness of and adherence to dietary therapy, ophthalmologic examination for the detection of cataracts and assessment of speech, with the possibility of speech therapy if developmental verbal dyspraxia is evident.

Patients with propionic acidemia should be started as early as possible on a low protein diet. In addition to a protein mixture that is devoid of methionine, threonine, valine, and isoleucine, the patient should also receive -carnitine treatment and should be given antibiotics 10 days per month in order to remove the intestinal propiogenic flora. The patient should have diet protocols prepared for him with a “well day diet” with low protein content, a “half emergency diet” containing half of the protein requirements, and an “emergency diet” with no protein content. These patients are under the risk of severe hyperammonemia during infections that can lead to comatose states.

Liver transplant is gaining a role in the management of these patients, with small series showing improved quality of life.

Metabolic disorders can be treatable by nutrition management, especially if detected early. It is important for dieticians to have knowledge of the genotype to therefore create a treatment that will be more effective for the individual.