Glycogen storage disease type 1a is an inherited condition in which the body cannot release its stored sugar back into the blood, so blood sugar falls dangerously low within a few hours of the last feed or meal [1,2].
This page provides general information. It does not replace advice from a doctor or another qualified healthcare professional.
Between meals the body runs on sugar it has already put aside. The liver keeps spare sugar in a packed form called glycogen, and releases it as glucose whenever the blood level starts to fall [3,6].
In GSD1a the final step of that release is missing. An enzyme called glucose-6-phosphatase does the last part, and without it the liver cannot hand its sugar over [1,6]. Two things follow. Blood sugar falls, sometimes within two to four hours of the last feed [1]. The sugar that is not released turns into more glycogen and into fat, which build up in the liver and kidneys and make them swell [2,6].
The condition is also called von Gierke disease and glucose-6-phosphatase deficiency [2,25].
GSD1a and GSD1b are not the same. Both are types of glycogen storage disease type I and both cause low blood sugar in the same way, so they are easily mixed up. Type 1a is caused by the G6PC1 gene and is about 80 percent of cases. Type 1b is caused by a different gene, SLC37A4, and only type 1b usually brings a low count of a white blood cell called a neutrophil, with repeated bacterial infections, mouth ulcers, gum disease and bowel inflammation [1,2,6]. Advice written for one type does not always fit the other.
Glycogen storage disease type I affects about 1 in 100,000 babies born [1,3,9]. Roughly 80 percent have type 1a, so type 1a alone is rarer than that figure suggests [2,3]. Orphanet records the prevalence, meaning the number of people living with it at any one time, as unknown [3,4].
The condition is found in every population, and is more common where one gene change has become frequent in a community. Among Ashkenazi Jewish people the estimated prevalence is about 1 in 20,000 [1,9]. About 88 percent of affected people of Japanese ancestry carry one particular change, which describes the pattern of changes there rather than how common the condition is [1].
Counts of real people are scarce. Hospital records in England identified 943 people with type 1a over just under six years [14]. Figures for much of Asia, Africa, the Middle East and South America are not published, and testing is unevenly available [3].
Genes are instructions inside our cells. GSD1a is caused by changes, also called variants, in a gene on chromosome 17 named G6PC1, previously written G6PC [3,6]. That gene carries the instructions for glucose-6-phosphatase, active in the liver, kidneys and intestines [6].
GSD1a is inherited in an autosomal recessive pattern. A child needs two changed copies, one from each parent. Parents who each carry a single changed copy are called carriers, and carriers are well [2]. Where both parents are carriers, each pregnancy carries a 25 percent chance of a child with the condition and a 50 percent chance of a carrier [1,3].
Brothers and sisters should be checked as early as possible, since starting treatment before damage occurs makes a real difference [1]. Where both gene changes in a family are known, carrier testing and testing in pregnancy are possible, and a genetic counselor can explain the options [1,3]. Nothing a parent did during pregnancy causes GSD1a.
Some newborns have very low blood sugar in the first days. More often the condition shows itself at around three to four months, when feeds are spaced further apart or a baby starts sleeping through the night [1,3].
When to seek urgent help. Low blood sugar is the central daily danger in GSD1a, and untreated it can cause seizures, brain injury or death [8,9]. Go straight to the nearest emergency department if a child with GSD1a is vomiting, will not feed, cannot keep cornstarch or fluids down, is unusually drowsy or hard to rouse, is confused, or has a seizure. Illness raises the need for glucose just as feeding becomes difficult, so a stomach bug that would be minor in another child is not minor here [8,9]. Treatment is glucose, by mouth or feeding tube if that is possible and into a vein if it is not [8]. Say the diagnosis straight away, show the emergency letter, and contact the specialist team [8].
Suspicion usually starts with a doctor who finds low blood sugar and a large liver in a baby. Care is then led by a metabolic specialist, with a dietitian and often a liver and a kidney doctor [1,8].
First come blood tests: glucose, lactate, uric acid, triglycerides, cholesterol and liver enzymes. In GSD1a, blood sugar can fall below 60 mg/dL after only three or four hours without food, while lactate rises rather than falls [1,8].
Diagnosis is confirmed by genetic testing of G6PC1, preferred to a liver biopsy because it avoids an operation and finds the responsible change in about 95 percent of people [1,3]. GSD1a is not on routine newborn screening panels, so it is found through symptoms or family testing, and diagnosis can be delayed where early signs are read as ordinary feeding problems [1,9].
There is no cure. Treatment keeps blood sugar steady around the clock, which prevents the immediate danger and reduces long-term damage. Guidelines recommend keeping blood glucose at or above 70 mg/dL and treating any level below 60 mg/dL [8].
Frequent carbohydrate. Small, frequent meals rich in slowly digested carbohydrate are spread across the whole day. Infants and young children should not go longer than three to four hours without carbohydrate, and older children and adults no longer than five to six hours [8].
Uncooked cornstarch. Raw cornstarch releases glucose slowly, and it is the backbone of treatment. It is usually tried between six and twelve months of age and built up gradually. Typical doses, set by the team, are about 1 to 1.6 grams per kilogram every three to four hours in young children, and 1.7 to 2.5 grams per kilogram every four to five hours in older children and adults [8,9]. It must not be cooked or mixed with hot water, which stops it working; cold water or a sugar-free, lactose-free drink is used instead [1,8]. An extended-release form is sold in many countries for overnight use [9].
Overnight feeding. Nights are the longest fast. Families either wake to give cornstarch or use a continuous feed through a nasogastric or gastrostomy tube. Both work, and the choice is a shared decision [9]. Both carry risk. A missed dose, a failed alarm, a blocked tube or a pump failure can cause severe low blood sugar, seizures or death, so two alarms, pump alarms and bed-wetting sensors are strongly advised, and parents are encouraged to take turns [8,9].
Sugars to avoid. Fructose, sucrose, galactose, lactose and sorbitol cannot be handled properly and add to the acid load, so table sugar, most fruit, juice, honey, syrups and most dairy are limited or avoided [1,8,9]. That leaves gaps, so a sugar-free multivitamin with minerals, calcium and vitamin D are essential [1,8].
Medicines and monitoring. Allopurinol for high uric acid, an ACE inhibitor when protein appears in the urine, citrate for kidney stones and lipid-lowering medicines from about age 10 may all be used [1,8]. Regular blood, liver, kidney and bone checks are recommended, and a liver transplant is considered when adenomas become worrying [1,3,22].
Life with GSD1a is built around a clock, and care works best through a metabolic center with a dietitian who knows the condition [1,9]. Every family should carry an emergency letter at all times, with copies at school, at work and in the car, reviewed each year [8]. An emergency kit holds the letter, contact numbers, a glucose meter with spare strips, water, cornstarch, glucose gel and a snack. Medical alert jewelry helps when a person cannot speak for themselves [8]. Fluids containing lactate, such as lactated Ringer’s solution, should not be given [8].
Home blood glucose checks are part of daily life, before meals and cornstarch, before and after exercise, and whenever illness or a low is suspected [8,9]. Fasting before an operation is not safe, so people with GSD1a are usually admitted the day before for glucose into a vein [8,15]. Complications can appear even with good control, so monitoring continues for life, and pregnancy needs planning, since some medicines must stop beforehand [1,9].
Broken sleep, fear of a missed dose, and worry about hospital visits are common, and worth naming to the care team [9].
Clinical trials are research studies that test whether a treatment works and is safe. In GSD1a, current care is dietary, and research is testing treatments aimed at the missing enzyme. Looking into a study is a personal choice, and for a child a family decision.
It is worth being clear about what a study actually involves:
Every trial has rules about who can take part. These are called eligibility criteria. Some describe who can join, and others who cannot. For a GSD1a study they might include a diagnosis confirmed by genetic testing of G6PC1, a minimum age, a stable cornstarch regimen, how well the liver and kidneys are working, the size or number of any liver adenomas, and previous gene therapy.
trialport’s medifit helps people consider information related to possible medical suitability. It does not diagnose a condition, confirm eligibility or replace formal screening by the study team.
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A study can look right on paper and still be hard in practice. Worth thinking through:
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Research is focused on replacing the missing enzyme rather than working around it:
Study status checked: 3 August 2026. Research moves and what is studied changes, so this list will date. For current information, search at app.trialport.com.
In the United States, the Association for Glycogen Storage Disease holds an annual family and clinician conference and publishes pages for each type [16]. The NIH Genetic and Rare Diseases Information Center offers a plain summary and a support line [7].
In the United Kingdom, AGSD-UK has a von Gierke section, a list of specialist centers and an annual conference [17], and Metabolic Support UK covers inherited metabolic conditions more broadly [18]. In Europe, MetabERN links expert centers across member states, and Orphanet lists centers, patient organizations and emergency guidance by country [3,19].
In Australia the Metabolic Dietary Disorders Association supports families with inherited metabolic conditions, in New Zealand Rare Disorders NZ is the national umbrella body, and in Canada that role falls to CORD [20,21,24]. Coverage in much of Asia, Africa, the Middle East and South America is thin, and a national rare disease organization or metabolic unit is the best next contact.
Is GSD1a curable?
No. Treatment keeps blood sugar steady and reduces damage, and it continues for life. Research aimed at the missing enzyme is active, and none of it is approved [8,11].
How long can a child with GSD1a safely go without food?
Less time than other children. Guidelines advise avoiding fasts longer than three to four hours in infants and young children, and five to six hours in adolescents and adults [8].
Why cornstarch rather than sugar?
Raw cornstarch is digested slowly, so it releases glucose over hours instead of minutes. Sugars such as sucrose and fructose cannot be handled properly in GSD1a [8,9].
What is the difference between GSD1a and GSD1b?
Different genes and different extra problems. Only type 1b usually causes a low neutrophil count, with repeated infections, mouth ulcers and bowel inflammation [2,6].
Will our other children have it?
Only if a child inherits a changed copy from both parents. Each pregnancy of two carriers carries a 25 percent chance, and testing brothers and sisters early is recommended [1,3].
Can someone with GSD1a live a normal life span?
Most people now live into adulthood with treatment started early, and adults have had successful pregnancies [1]. Liver adenomas and kidney problems can still develop, so the long-term outlook remains uncertain [1,9].
Written by: trialport editorial team
Reviewed by: Keith Berelowitz, Founder and CEO, trialport
Reviewed on: 3 August 2026
Next review due: 3 August 2027
References last checked: 3 August 2026