Xylose isomerase acts to convert fructose sugars into glucose. Dietary supplements of xylose isomerase may improve the symptoms of fructose malabsorption.

There is no known cure, but an appropriate diet and the enzyme xylose isomerase can help. The ingestion of glucose simultaneously with fructose improves fructose absorption and may prevent the development of symptoms. For example, people may tolerate fruits such as grapefruits or bananas, which contain similar amounts of fructose and glucose, but apples are not tolerated because they contain high levels of fructose and lower levels of glucose.

Treatment of HFI depends on the stage of the disease, and the severity of the symptoms. Stable patients without acute intoxication events are treated by careful dietary planning that avoids fructose and its metabolic precursors. Fructose is replaced in the diet by glucose, maltose or other sugars. Management of patients with HFI often involves dietitians who have a thorough knowledge of what foods are acceptable.

The primary treatment method for fatty-acid metabolism disorders is dietary modification. It is essential that the blood-glucose levels remain at adequate levels to prevent the body from moving fat to the liver for energy. This involves snacking on low-fat, high-carbohydrate nutrients every 2–6 hours. However, some adults and children can sleep for 8–10 hours through the night without snacking.

Treatment is directed largely towards management of underlying cause:

- Replacement of nutrients, electrolytes and fluid may be necessary. In severe deficiency, hospital admission may be required for nutritional support and detailed advice from dietitians. Use of enteral nutrition by naso-gastric or other feeding tubes may be able to provide sufficient nutritional supplementation. Tube placement may also be done by percutaneous endoscopic gastrostomy, or surgical jejunostomy. In patients whose intestinal absorptive surface is severely limited from disease or surgery, long term total parenteral nutrition may be needed.

- Pancreatic enzymes are supplemented orally in pancreatic insufficiency.

- Dietary modification is important in some conditions:

- Gluten-free diet in coeliac disease.

- Lactose avoidance in lactose intolerance.

- Antibiotic therapy to treat Small Bowel Bacterial overgrowth.

- Cholestyramine or other bile acid sequestrants will help reducing diarrhoea in bile acid malabsorption.

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.

To treat people with a deficiency of this enzyme, they must avoid needing gluconeogenesis to make glucose. This can be accomplished by not fasting for long periods, and eating high-carbohydrate food. They should avoid fructose containing foods (as well as sucrose which breaks down to fructose).

As with all single-gene metabolic disorders, there is always hope for genetic therapy, inserting a healthy copy of the gene into existing liver cells.

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.

The goal for treatment of GSD type 0 is to avoid hypoglycemia. This is accomplished by avoiding fasting by eating every 3-4 hours during the day. At night, uncooked corn starch can be given because it is a complex glucose polymer. This will be acted on slowly by pancreatic amylase and glucose will be absorbed over a 6 hour period.

There is no broadly accepted standard of care for infants with DG. Some healthcare providers recommend partial to complete dietary restriction of milk and other high galactose foods for infants or young children with DG; others do not. Because children with DG develop increased tolerance for dietary galactose as they grow, few healthcare providers recommend dietary restriction of lactose or galactose beyond early childhood.

The rationale for NOT restricting dietary galactose exposure of infants and/or young children with DG: Healthcare providers who do not recommend dietary restriction of galactose for infants with DG generally consider DG to be of no clinical significance—meaning most infants and children with DG seem to be doing clinically well. Further, these providers may be opposed to interrupting or reducing breastfeeding when there is no clear evidence it is contraindicated. These providers may argue that the recognized health benefits of breastfeeding outweigh the potential risks of as yet unknown negative effects of continued milk exposure for these infants. For infants with DG who continue to drink milk, some doctors would recommend that blood galactose-1-phosphate (Gal-1P) or urinary galactitol be rechecked by age 12 months to ensure that these metabolite levels are normalizing.

The rationale FOR restricting dietary galactose exposure of infants and/or young children with DG: Healthcare providers who recommend partial or complete dietary restriction of galactose for infants and/or young children with DG generally cite concern about the unknown long-term consequences of abnormally elevated galactose metabolites in a young child's blood and tissues. Infants with DG who continue to drink milk accumulate the same set of abnormal galactose metabolites seen in babies with classic galactosemia – e.g. galactose, Gal-1P, galactonate, and galactitol – but to a lesser extent. While it remains unclear whether any of these metabolites contribute to the long-term developmental complications experienced by so many older children with classic galactosemia, the possibility that they might cause problems serves to motivate some healthcare providers to recommend dietary galactose restriction for infants with DG. Switching an infant with DG from milk or milk formula (high galactose) to soy formula (low galactose) rapidly normalizes their galactose metabolites. This approach is considered potentially preventative rather than responsive to acute symptoms.

If dietary galactose restriction of any kind is followed, healthcare providers may recommend that the child have a galactose challenge to re-evaluate galactose tolerance before the restrictive diet is discontinued. Most infants or young children with DG who are followed by a metabolic specialist are discharged from follow up after a successful galactose challenge.Options for those choosing to restrict dietary galactose in infancy and/or early childhood: Dietary restriction practices for Duarte galactosemia vary widely. In the US, some healthcare providers recommend full dietary restriction of milk and all dairy products for the first 12 months of life, followed by a galactose challenge. Some providers recommend the galactose challenge before 12 months, others after. Some providers who recommend dietary intervention suggest a "compromise approach" if the parent wishes to breastfeed, such that the parent alternates feedings of breast milk and low galactose formula. Finally, some parents choose to continue some form of dietary galactose restriction for their child with DG beyond early childhood.

What is a galactose challenge? The goal of a galactose challenge is to learn whether a child is able to metabolize dietary galactose sufficiently to prevent the abnormal accumulation of galactose metabolites, generally measured as Gal-1P in the blood. For infants with DG who showed elevated galactose metabolites at diagnosis, this test can be used to see if their ability to process galactose has improved enough to discontinue dietary galactose restriction.

To test galactose metabolism, a baseline Gal-1P level is measured while the child is on a galactose-restricted diet. If the level is within the normal range (e.g. <1.0 mg/dL), the parent/guardian is advised to "challenge" the child with dietary galactose—meaning feed the child a diet that includes normal levels of milk for 2–4 weeks. Immediately after that time, another blood sample is collected and analyzed for Gal-1P level. If this second result is still in the normal range, the child is said to have "passed" their galactose challenge, and dietary galactose restrictions are typically relaxed or discontinued. If the second test shows elevated Gal-1P levels, the parent/guardian may be advised to resume galactose restriction for the child, and the "challenge" may be repeated after a few months.

It is important for MADD patients to maintain strength and fitness without exercising or working to exhaustion. Learning this balance may be more difficult than normally, as muscle pain and fatigue may be perceived differently from normal individuals.

Symptomatic relief from the effects of MADD may sometimes be achieved by administering ribose orally at a dose of approximately 10 grams per 100 pounds (0.2 g/kg) of body weight per day, and exercise modulation as appropriate. Taken hourly, ribose provides a direct but limited source of energy for the cells. Patients with myoadenylate deaminase deficiency do not retain ribose during heavy exercise, so supplementation may be required to rebuild levels of ATP.

Creatine monohydrate could also be helpful for AMPD patients, as it provides an alternative source of energy for anaerobic muscle tissue and was found to be helpful in the treatment of other, unrelated muscular myopathies.

Intake of carbohydrates which must be converted to G6P to be utilized (e.g., galactose and fructose) should be minimized. Although elemental formulas are available for infants, many foods contain fructose or galactose in the forms of sucrose or lactose. Adherence becomes a contentious treatment issue after infancy.

The only treatment for classic galactosemia is eliminating lactose and galactose from the diet. Even with an early diagnosis and a restricted diet, however, some individuals with galactosemia experience long-term complications such as speech difficulties, learning disabilities, neurological impairment (e.g. tremors, etc.), and ovarian failure. Symptoms have not been associated with Duarte galactosemia, and many individuals with Duarte galactosemia do not need to restrict their diet at all. However, research corroborates a previously overlooked theory that Duarte galactosemia may lead to language developmental issues in children with no clinical symptoms. Infants with classic galactosemia cannot be breast-fed due to lactose in human breast milk and are usually fed a soy-based formula.

Galactosemia is sometimes confused with lactose intolerance, but galactosemia is a more serious condition. Lactose intolerant individuals have an acquired or inherited shortage of the enzyme lactase, and experience abdominal pains after ingesting dairy products, but no long-term effects. In contrast, a galactosemic individual who consumes galactose can cause permanent damage to their bodies.

Long term complication of galactosemia includes:

- Speech deficits

- Ataxia

- Dysmetria

- Diminished bone density

- Premature ovarian failure

- Cataract

The primary treatment goal is prevention of hypoglycemia and the secondary metabolic derangements by frequent feedings of foods high in glucose or starch (which is readily digested to glucose). To compensate for the inability of the liver to provide sugar, the total amount of dietary carbohydrate should approximate the 24-hour glucose production rate. The diet should contain approximately 65–70% carbohydrate, 10–15% protein, and 20–25% fat. At least a third of the carbohydrates should be supplied through the night, so that a young child goes no more than 3–4 hours without carbohydrate intake

In the last 30 years, two methods have been used to achieve this goal in young children: (1) continuous nocturnal gastric infusion of glucose or starch; and (2) night-time feedings of uncooked cornstarch. An elemental formula, glucose polymer, and/or cornstarch can be infused continuously through the night at a rate supplying 0.5–0.6 g/kg/h of glucose for an infant, or 0.3–0.4 for an older child. This method requires a nasogastric or gastrostomy tube and pump. Sudden death from hypoglycemia has occurred due to malfunction or disconnection, and periodic cornstarch feedings are now preferred to continuous infusion.

Cornstarch is an inexpensive way to provide gradually digested glucose. One tablespoon contains nearly 9 g carbohydrate (36 calories). Although it is safer, less expensive, and requires no equipment, this method does require that parents arise every 3–4 hours to administer the cornstarch. A typical requirement for a young child is 1.6 g/kg every 4 hours.

Long-term management should eliminate hypoglycemic symptoms and maintain normal growth. Treatment should achieve normal glucose, lactic acid, and electrolyte levels, and only mild elevations of uric acid and triglycerides.

Ketosis is deliberately induced by use of a ketogenic diet as a medical intervention in cases of intractable epilepsy. Other uses of low-carbohydrate diets remain controversial. Carbohydrate deprivation to the point of ketosis has been argued to have both negative and positive effects on health.

Because of the ease of therapy (dietary exclusion of fructose), HFI can be effectively managed if properly diagnosed. In HFI, the diagnosis of homozygotes is difficult, requiring a genomic DNA screening with allele specific probes or an enzyme assay from a liver biopsy. Once identified, parents of infants who carry mutant aldolase B alleles leading to HFI, or older individuals who have clinical histories compatible with HFI can be identified and counselled with regard to preventive therapy: dietary exclusion of foods containing fructose, sucrose, or sorbitol. If possible, individuals who suspect they might have HFI, should avoid testing via fructose challenge as the results are non-conclusive for individuals with HFI and even if the diagnostic administration fructose is properly controlled, profound hypoglycemia and its sequelae can threaten the patient's well-being.

Once ketotic hypoglycemia is suspected and other conditions excluded, appropriate treatment reduces the frequency and duration of episodes. Extended fasts should be avoided. The child should be given a bedtime snack of carbohydrates (e.g. spaghetti or pasta or milk) and should be awakened and fed after the usual duration of sleep. If the child is underweight, a daily nutritional supplement may be recommended. Raw cornstarch dissolved in a beverage helps individuals with hypoglycemia, especially that caused by Glycogen Storage Disease, sustain their blood sugars for longer periods of time and may be given at bedtime.

If a spell begins, carbohydrates and fluids should be given promptly. If vomiting prevents this, the child should be taken to the local emergency department for a few hours of intravenous saline and dextrose. This treatment is often expedited by supplying the parents with a letter describing the condition and recommended treatment.

Management for mitochondrial trifunctional protein deficiency entails the following:

- Avoiding factors that might precipitate condition

- Glucose

- Low fat/high carbohydrate nutrition

Treatment for glycogen storage disease type III may involve a high-protein diet, in order to facilitate gluconeogenesis. Additionally the individual may need:

- IV glucose (if oral route is inadvisable)

- Nutritional specialist

- Vitamin D (for osteoporosis/secondary complication)

- Hepatic transplant (if complication occurs)

Treatments for Glycerol Kinase Deficiency are targeted to treat the symptoms because there are no permanent treatments for this disease. The main way to treat these symptoms is by using corticosteroids, glucose infusion, or mineralocorticoids. Corticosteroids are steroid hormones that are naturally produced in the adrenal glands. These hormones regulate stress responses, carbohydrate metabolism, blood electrolyte levels, as well as other uses. The mineralocorticoids, such as aldosterone control many electrolyte levels and allow the kidneys to retain sodium. Glucose infusion is coupled with insulin infusion to monitor blood glucose levels and keep them stable.

Due to the multitude of varying symptoms of this disease, there is no specific treatment that will cure this disease altogether. The symptoms can be treated with many different treatments and combinations of medicines to try to find the correct combination to offset the specific symptoms. Everyone with Glycerol Kinase Deficiency has varying degrees of symptoms and thereby requires different medicines to be used in combination to treat the symptoms; however, this disease is not curable and the symptoms can only be managed, not treated fully.

Refeeding syndrome can be fatal if not recognized and treated properly. An awareness of the condition and a high index of suspicion are required in order to make the diagnosis. The electrolyte disturbances of the refeeding syndrome can occur within the first few days of refeeding. Close monitoring of blood biochemistry is therefore necessary in the early refeeding period. In critically ill patients admitted to an intensive care unit, if phosphate drops to below 0.65 mmol from a previously normal level within three days of starting enteral or parenteral nutrition, caloric intake should be reduced to 480 kcals per day for at least two days whilst electrolytes are replaced. Prescribing thiamine, vitamin B complex (strong) and a multivitamin and mineral preparation is recommended. Biochemistry should be monitored regularly until it is stable. Although clinical trials are lacking in patients other than those admitted to an intensive care, it is commonly recommended that energy intake should remain lower than that normally required for the first 3–5 days of treatment of refeeding syndrome.

See NICE Clinical guideline CG32, section 6.6. On first aid and preliminary medical management, see for example the guidance by HMS Monmouth medical officer.

To relieve reactive hypoglycemia, the NIH recommends taking the following steps:

- Avoiding or limiting sugar intake;

- Exercising regularly; exercise increases sugar uptake which decreases excessive insulin release

- Eating a variety of foods, including meat, poultry, fish, or nonmeat sources of protein, foods such as whole-grains, fruits, nuts, vegetables, and dairy products;

- Choosing high-fiber foods.

Other tips to prevent sugar crashes include:

- Avoiding eating meals or snacks composed entirely of carbohydrates; simultaneously ingest fats and proteins, which have slower rates of absorption.

- Consistently choosing longer lasting, complex carbohydrates to prevent rapid blood-sugar dips in the event that one does consume a disproportionately large amount of carbohydrates with a meal

- Monitoring any effects medication may have on symptoms.

Low-carbohydrate diet and/or frequent small split meals is the first treatment of this condition. The first important point is to add small meals at the middle of the morning and of the afternoon, when glycemia would start to decrease. If adequate composition of the meal is found, the fall in blood glucose is thus prevented. Patients should avoid rapidly absorbable sugars and thus avoid popular soft drinks rich in glucose or sucrose. They should also be cautious with drinks associating sugar and alcohol, mainly in the fasting state.

As it is a short-term ailment, a sugar crash does not usually require medical intervention in most people. The most important factors to consider when addressing this issue are the composition and timing of foods.

Acute low blood sugar symptoms are best treated by consuming small amounts of sweet foods, so as to regain balance in the body’s carbohydrate metabolism. Suggestions include sugary foods that are quickly digested, such as:

- Dried fruit

- Soft drinks

- Juice

- Sugar as sweets, tablets or cubes.

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.

Some clinicians regard eliminating carbohydrates as unhealthy and dangerous. However, it is not necessary to eliminate carbohydrates from the diet completely to achieve ketosis. Other clinicians regard ketosis as a safe biochemical process that occurs during the fat-burning state. Ketosis, which is accompanied by gluconeogenesis (the creation of glucose de novo from pyruvate), is the specific state that concerns some clinicians. However, it is unlikely for a normally functioning person to reach life-threatening levels of ketosis, defined as serum beta-hydroxybutyrate (B-OHB) levels above 15 millimolar (mM) compared to ketogenic diets among non diabetics, which "rarely run serum B-OHB levels above 3 mM." This is avoided with proper basal secretion of pancreatic insulin. People who are unable to secrete basal insulin, such as type 1 diabetics and long-term type II diabetics, are liable to enter an unsafe level of ketosis, eventually resulting in a coma that requires emergency medical treatment. The anti-ketosis conclusions have been challenged by a number of doctors and advocates of low-carbohydrate diets, who dispute assertions that the body has a preference for glucose and that there are dangers associated with ketosis.

Children "outgrow" ketotic hypoglycemia, presumably because fasting tolerance improves as body mass increases. In most the episodes become milder and more infrequent by 4 to 5 years of age and rarely occur after age 9. Onset of hypoglycemia with ketosis after age 5 or persistence after age 7 should elicit referral and an intensive search for a more specific disease.