Understanding Insulinoma: Symptoms, Causes, and Recovery
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer: What Is Insulinoma?
An insulinoma is a rare type of pancreatic neuroendocrine tumor that starts in the pancreas's endocrine cells and overproduces insulin, the hormone that regulates blood glucose. [1] The excess insulin drives blood sugar dangerously low, causing symptoms that range from shakiness to seizures. [1] About 85% to 90% of these tumors do not spread to other parts of the body. [1]
What the research says
Most insulinomas are small, benign and single, and surgery usually cures them. A systematic review of 114 articles (6,222 cases) found that insulinomas were mostly sporadic (94%), benign (87%), single (90%) and smaller than 20 mm (84%). Enucleation was the most common operation (56%), followed by distal pancreatectomy (32%) and the Whipple procedure (3%). The tumor returned in 7% of patients after surgery (Mehrabi et al., Pancreas, 2014) [2].
Long-term survival is normal for non-metastatic insulinoma but not for metastatic disease. In a Finnish cohort of 79 patients compared with 316 matched controls (median follow-up about 11 years), survival of the 70 patients with non-metastatic insulinoma was similar to controls, while the 9 patients with distant metastases had a median survival of 3.4 years. Atrial fibrillation was more common in patients (rate ratio 2.07, 95% CI 1.02-4.22) (Peltola et al., European Journal of Endocrinology, 2021) [3].
Malignant insulinoma is extremely rare, and surgery is linked to better survival. A US registry study of 121 patients with malignant insulinoma found an annual incidence of 0.0-0.27 cases per million person-years. At diagnosis, 40% had localized disease and 39% had distant metastases. Median cancer-specific survival was 183 months, and surgical resection, male sex and absence of metastases were linked to better survival (Sada et al., World Journal of Surgery, 2020) [4].
Key Takeaways
What is an insulinoma?
Insulinoma represents a specific category of pancreatic neuroendocrine tumors that disrupt the body’s natural glucose regulation. Unlike standard pancreatic cells that release insulin only when blood sugar rises, the cells within an insulinoma release the hormone continuously and excessively. This constant flood of insulin forces blood sugar levels to drop, even when the body has not recently consumed food.
Most insulinomas are “indolent,” meaning they grow slowly and remain confined to the pancreas. In rare instances, roughly 10% to 15% of cases, the tumor may become “aggressive” or metastatic, spreading to nearby lymph nodes or the liver. [1] Regardless of its classification, the primary health challenge remains the management of chronic and severe low blood sugar episodes.
What are the symptoms of an insulinoma?
The symptoms of insulinoma are directly tied to the resulting hypoglycemia. These episodes often occur during periods of fasting or exercise when the body’s glucose demands are higher.
Severe hypoglycemia can be life-threatening if left untreated, making early recognition of these signs critical for patient safety. At the first signs, take a fast-acting sugar such as juice or glucose tablets; if someone is confused, unconscious or having a seizure, call 911. [1]
What causes an insulinoma, and what are the risk factors?
Most insulinomas occur sporadically, meaning they happen for no identifiable reason and are not linked to specific lifestyle choices. However, a small percentage of cases are associated with a genetic condition known as multiple endocrine neoplasia type 1 (MEN1). [1] This inherited syndrome increases the likelihood of developing various endocrine tumors, including those in the pancreas, parathyroid, and pituitary glands.
How is an insulinoma diagnosed?
Diagnosing an insulinoma requires a combination of clinical observation and advanced testing. Because the tumor is rare and its symptoms mimic other conditions, a systematic approach is necessary.
The 72-Hour Fast: This is considered the gold standard for diagnosis. [1] Under strict medical supervision, a patient fasts to induce a low blood sugar episode, allowing doctors to measure insulin and glucose levels simultaneously.
Laboratory Testing: Blood draws check for insulin, C-peptide, and proinsulin levels. [1] High levels of these markers during a hypoglycemic episode strongly suggest the presence of an insulinoma.
Imaging and Localization: Once biochemical evidence is confirmed, imaging tests like CT scans, MRIs, or endoscopic ultrasounds are used to pinpoint the tumor’s exact location within the pancreas. [1]
How is an insulinoma treated and managed?
The primary goal of treating an insulinoma is to stop the overproduction of insulin and restore normal blood sugar levels.
Surgical Interventions
Surgery is the most effective treatment and offers a permanent cure for most patients. [1]
Enucleation: If the tumor is small and near the surface, surgeons may remove only the tumor itself, sparing the rest of the pancreatic tissue.
Partial Pancreatectomy: In cases where the tumor is deeper or larger, a portion of the pancreas may be removed.
Whipple Procedure: This more extensive surgery may be needed in rare cases, such as metastatic disease involving the head of the pancreas and surrounding structures.
Medical and Dietary Management
For patients awaiting surgery or those who are not surgical candidates, other strategies are employed:
What is the long-term outlook for an insulinoma?
The prognosis for individuals with non-metastatic insulinoma is excellent. [3] Surgical removal typically results in a complete cure, and in one study about 87% of people who had surgery for non-metastatic insulinoma were alive 10 years after diagnosis. [1] For the rare cases of metastatic insulinoma, the outlook is more complex, requiring a multidisciplinary approach that may involve chemotherapy, targeted therapy, and specialized radionuclide treatments. [1]
Conclusion
Insulinoma is a challenging but highly treatable condition. By understanding the link between pancreatic tumors and insulin overproduction, patients and healthcare providers can work together to achieve a surgical cure and return to a life free from the dangers of chronic hypoglycemia.
Frequently Asked Questions
What is an insulinoma?
A rare pancreatic tumor that produces too much insulin. [1]
Is insulinoma cancerous?
What is the main symptom?
Low blood sugar (hypoglycemia). [1]
Why does it cause low blood sugar?
It releases insulin regardless of the body’s glucose levels.
How rare is it?
It is estimated to occur in only 1 to 4 people per million annually.
Can it be cured?
What is the 72-hour fast?
A supervised test to trigger and measure hypoglycemia. [1]
Who gets insulinomas?
Anyone can, though reports differ on whether it is more common in women or men.
What age is it usually diagnosed?
Mostly in the fifth decade of life. [2]
Is it hereditary?
What is MEN1?
A genetic disorder causing multiple endocrine tumors. [1]
Can insulinoma cause seizures?
Yes, due to severe low blood sugar. [1]
What is enucleation?
Removing just the tumor without cutting into it, sparing the rest of the pancreas. [1]
What is a pancreatectomy?
Removing part or all of the pancreas.
What is diazoxide used for?
To help control how much insulin the pancreas releases. [1]
Can diet manage it?
Diet helps manage symptoms but doesn’t remove the tumor.
What are pNETs?
Pancreatic neuroendocrine tumors.
Does it spread?
Only in a small minority of cases (roughly 10% to 15%). [1]
Where does it spread?
Usually to the liver or lymph nodes. [1]
Is weight gain common?
It can be, because people often eat more to avoid low blood sugar.
Can it be seen on a CT scan?
Usually, though some small tumors are hard to find.
What is an endoscopic ultrasound?
A procedure using a scope to get close-up images of the pancreas.
What is C-peptide?
A substance produced along with insulin; high levels during low blood sugar help confirm the diagnosis.
Are there non-surgical treatments?
Yes, but they are usually for symptom control or metastatic cases.
What is PRRT?
Peptide receptor radionuclide therapy, a targeted radiation therapy for neuroendocrine tumors.
How long is recovery after surgery?
Usually several weeks depending on the type of surgery.
Can insulinoma return?
It is uncommon but possible, especially in MEN1 cases.
Does it affect digestion?
Usually not, unless a large part of the pancreas is removed.
What is the survival rate?
About 87% of people who had surgery for non-metastatic insulinoma were alive 10 years after diagnosis in one study. [1]
Can children get it?
It is extremely rare in children.
What happens if left untreated?
Severe hypoglycemia can lead to coma or death. [1]
Is it the same as diabetes?
No, it’s the opposite; it causes too much insulin, not too little.
Can it cause fainting?
Yes, “syncope” is a common symptom of low blood sugar.
What are complex carbohydrates?
Foods like whole grains that provide steady energy.
Why wear a medical ID?
To alert emergency responders to hypoglycemia risk. [1]
Is chemotherapy used?
Only for metastatic or aggressive cases.
What is targeted therapy?
Drugs that attack specific cancer cells.
Can exercise trigger symptoms?
Yes, physical activity lowers blood sugar further.
Is a biopsy always needed?
Not always; diagnosis is often made via blood tests and imaging.
What is the duodenum?
The first part of the small intestine, located near the pancreas.
Does it cause pain?
Usually not; symptoms are metabolic rather than painful.
Can it be misdiagnosed?
Yes, often as epilepsy or psychiatric disorders.
What is glucagon?
A hormone that raises blood sugar, sometimes used in treatment.
Is the surgery laparoscopic?
Sometimes. Open surgery is still the most common approach [2], but minimally invasive approaches are used depending on the tumor’s location and size.
What is indolent?
A term meaning slow-growing and non-aggressive.
What are endocrine cells?
Cells that produce and release hormones.
Can I drive with an insulinoma?
It may be restricted until hypoglycemia is controlled.
Is it preventable?
No, as most cases are sporadic or genetic.
What is the Whipple surgery?
A complex surgery removing the head of the pancreas and nearby organs.
Should I see a specialist?
Yes, an endocrinologist or surgical oncologist is recommended.
Related Reading
Blood Glucose Test: Normal Blood Sugar Levels, Prediabetes and Diabetes Ranges explains normal, prediabetes and diabetes blood sugar ranges.
C-Peptide Test: Purpose, Normal Range and What High or Low Results Mean explains the blood test that shows how much insulin your pancreas still makes.
References
Cleveland Clinic. Insulinoma: What It Is, Causes, Symptoms & Treatment. Cleveland Clinic. Last updated November 21, 2024. https://my.clevelandclinic.org/health/diseases/22217-insulinoma
Mehrabi A, Fischer L, Hafezi M, et al. A systematic review of localization, surgical treatment options, and outcome of insulinoma. Pancreas. 2014;43(5):675-686. PMID: 24921202. https://doi.org/10.1097/MPA.0000000000000110
Peltola E, Hannula P, Huhtala H, et al. Long-term morbidity and mortality in patients diagnosed with an insulinoma. European Journal of Endocrinology. 2021;185(4):577-586. PMID: 34374651. https://doi.org/10.1530/EJE-21-0230
Sada A, Glasgow AE, Vella A, et al. Malignant Insulinoma: A Rare Form of Neuroendocrine Tumor. World Journal of Surgery. 2020;44(7):2288-2294. PMID: 32128613. https://doi.org/10.1007/s00268-020-05445-x
Disclaimer
This article is for informational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional for diagnosis and treatment of any medical condition.
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