Symptoms of Insulinoma

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Insulinomas are rare tumors that form in the pancreas, an organ that regulates the production of certain enzymes and hormones. The hormone that is primarily affected by this condition is insulin, which controls blood sugar levels.

An insulinoma tumor tends to be small and is usually noncancerous. The tumor may cause excess insulin to be produced, even when blood sugar is low.

Doctor explaining lab results to patient

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Symptoms of insulinoma tend to appear when blood sugar starts to dip too low. The most common symptoms of insulinoma include trouble concentrating, weakness, shakiness, mood swings, and sweating.

This article will review common and rare symptoms of insulinomas to watch out for.

Frequent Symptoms

Insulinoma causes changes in your endocrine system (the system that controls your hormone levels). Usually, your body regulates your insulin level depending on how much sugar is in your blood. When your blood sugar increases after eating, insulin is released to transport sugar into cells to be used for energy. As blood sugar goes down, your body stops releasing insulin until your next meal.

An insulinoma interrupts this natural regulation, leading to excess insulin and dangerously low blood sugar levels. Common symptoms of insulinoma include:

  • Anxiety, mood swings, and irritability: Glucose is the preferred type of energy for your brain and central nervous system. So when your blood sugar starts to dip, you may feel more irritable and experience mood changes.
  • Blurred vision or double vision: Impaired brain function due to low blood sugar can also cause changes to your vision, leading to blurry vision or double vision.
  • Confusion or trouble concentrating: When your blood sugar dips too low, brain cells don't work properly, making it more difficult to concentrate or causing confusion.
  • Weakness: Your muscles use glucose for energy. When there isn’t enough energy to move, you may feel weak or tired.
  • Sweating and tremors: When your blood sugar dips low, the body releases adrenaline, which can lead to sweating and shakiness.
  • Hunger: You may feel hungry with an insulinoma because low blood sugar may signal you to eat more food.
  • Sudden weight gain: With an insulinoma, you may need to eat more food to prevent dangerously low blood sugar. The excess insulin brings those extra calories into the cells and stores what isn’t used as fat.

Rare Symptoms

Insulinoma may lead to less common and more serious symptoms because it may impact the nervous system and trigger a stress response. Here are some of the rare symptoms of insulinoma:

  • Seizure-like activity: Insulinoma symptoms can sometimes mimic epilepsy, leading to seizure-like symptoms and convulsions.
  • Rapid heart rate: Low blood sugar can trigger a stress response from the adrenal glands, which release hormones like epinephrine and norepinephrine. These hormones lead to a rapid heart rate and heart palpitations.
  • Loss of consciousness or coma: Dangerously low blood sugar levels can lead to loss of consciousness and coma. Extremely low blood sugar can even lead to death.
  • Growth or spread of tumor: Malignant (cancerous) insulinoma is extremely rare. Only four people per 1 million develop insulinoma per year, and less than 10% of those cases are malignant. In these cases, the tumor may continue growing or spread to other parts of the body, such as the liver or intestines.


The complications that can develop from insulinoma can include infection or problems following surgery. Most insulinomas are treated with surgery to remove the tumor. Here are some of the possible complications of insulinoma:

  • Pancreatic fistula: A pancreatic fistula is an abnormal connection between the pancreas and another part of the body. This leads to digestive enzymes and pancreatic fluid leaking into other tissue. Pancreatic fistulas may be treated with surgical drains to remove the fluid.
  • Pseudocysts: A pseudocyst is a pocket made of scar tissue instead of pancreas cells. These can develop after an injury or when pancreatic fluids leak. Pseudocysts can be treated with monitoring (to see if they resolve or progress) and surgery to drain them.
  • Abscess: A pancreatic abscess is a collection of fluid or pus that can be from an infection or can be noninfectious.

When to See a Doctor

If you regularly experience symptoms of low blood sugar, it’s best to schedule an appointment with your healthcare provider. It’s important to understand the cause of low blood sugar to create an effective management and treatment plan to prevent complications.

Most cases of insulinoma require surgery to remove the tumor. After surgery, symptoms usually resolve completely.

Seek immediate medical attention if you’re experiencing any of the following symptoms. These could be a sign of dangerously low blood sugar or another medical emergency:

  • Confusion
  • Changes in vision—double vision or blurry vision
  • Sudden weakness
  • Loss of consciousness or passing out
  • Seizure-like activity

A Word From Verywell

Navigating a new health diagnosis can feel overwhelming. Your healthcare provider can help you understand your symptoms and create a treatment plan. They may recommend that you always keep snacks with you, such as juice or fruit, to consume if you start noticing the symptoms of low blood sugar.

Once the insulinoma is removed, most people are able to return to life as normal without symptoms.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Zhuo F, Anastasopoulou C. Insulinoma. In: StatPearls. StatPearls Publishing; 2021.

  2. Okabayashi T, Shima Y, Sumiyoshi T, et al. Diagnosis and management of insulinoma. World J Gastroenterol. 2013;19(6):829-837. doi: 10.3748/wjg.v19.i6.829

  3. Liu Q, Duan J, Zheng Y, Luo J, Cai X, Tan H. Rare malignant insulinoma with multiple liver metastases derived from ectopic pancreas: 3-year follow-up and literature review. Onco Targets Ther. 2018;11:1813-1819. doi: 10.2147/OTT.S154991

  4. Unegbu FC, Anjum F. Pancreatic fistula. In: StatPearls. StatPearls Publishing; 2021.

By Ashley Braun, MPH, RD
Ashley Braun, MPH, RD, is a registered dietitian and public health professional with over 5 years of experience educating people on health-related topics using evidence-based information. Her experience includes educating on a wide range of conditions, including diabetes, heart disease, HIV, neurological conditions, and more.