Medically Reviewed by Michael Dansinger, MD on August 15, 2022
4 min read

An insulinoma is a rare tumor of the pancreas. It’s made of cells called beta islet cells, the same ones in the pancreas that make insulin and control your blood sugar. Normally, your pancreas makes more insulin when your blood sugar is high and less when your blood sugar is low. But an insulinoma makes insulin all the time, even when your blood sugar gets too low.

You might hear an insulinoma called a "neuroendocrine tumor" because it starts in special cells in your body called neuroendocrine cells. These tumors are usually small (less than an inch), and almost all of them aren’t cancer. In most cases, surgery can cure them.

Because insulinomas make too much insulin, they can cause symptoms of low blood sugar, also known as hypoglycemia. You might have:

Hypoglycemia can be dangerous. If your blood sugar drops too low, you could faint or go into a coma.

Hypoglycemia is common in people with diabetes. It often happens because they took too much of their medicine, missed a meal, or got more exercise than usual, all of which can lower blood sugar. An insulinoma can also cause hypoglycemia when you haven’t eaten in a while, but it can happen at any time.

It isn’t clear why some people get insulinomas. Women are slightly more likely to have them than men. Most people get them between ages 40 and 60. You’re also more likely to have an insulinoma if you have certain genetic conditions, including:

  • Multiple endocrine neoplasia type 1: When tumors grow in glands that make hormones
  • Von Hippel-Lindau syndrome: When tumors and cysts grow in many organs throughout the body
  • Neurofibromatosis type 1: Noncancerous tumors in the nerves and skin
  • Tuberous sclerosis: Noncancerous tumors that grow in organs like your brain, eyes, heart, kidneys, skin, and lungs

It can be tough for doctors to diagnose an insulinoma. Its symptoms are the same as those of other common health problems. It may take time before your doctor can find it. You’ll get tests like:

Blood tests and suppression tests. To find out if you have an insulinoma, your doctor will test your blood sugar, insulin, C-peptide, and proinsulin during a 72-hour rest. This will confirm that:

  • You have symptoms of low blood sugar, especially after not eating or heavy exercise
  • Your blood sugar is actually low when you have those symptoms
  • Your symptoms go away after your blood sugar goes up

To do that, they’ll watch what happens to your blood sugar after you fast for a day or two. You may need to stay in the hospital during this time, and you won’t be able to eat or drink anything except water. The doctor will test your blood to see if you have both low blood sugar and a high insulin level.

Imaging tests. You may also get an imaging test such as a CT scan, ultrasound, or MRI so your doctor can see where the tumor is.

The main treatment for an insulinoma is surgery to remove the tumor. Most of the time, that will cure you.

The type of surgery you get depends on the type, size, and location of the tumor. Surgeons can usually remove just the insulinoma from the surface of your pancreas. Other times, the surgeon may need to remove part of the pancreas connected to the tumor. But this is less common.

You might be able to have laparoscopic surgery to remove an insulinoma. In this operation, doctors make several smaller cuts in your body instead of one large one. They use special instruments to do the surgery. That means you’ll have less pain as you heal, stay fewer days in the hospital, and can return to normal life more quickly.

Most people won’t need any more treatment after surgery.

If your doctor thinks surgery won’t work for you, you can try other treatments to manage low blood sugar. You might take medicine and eat smaller meals more often throughout the day.

Treatment for cancerous insulinomas

Cancerous insulinomas are rare, and they need different treatment. If your doctor can’t remove the whole tumor, you may need to take medicine to prevent low blood sugar. You may also need chemotherapy. Depending on the type of tumor you have, another treatment is getting a radioactive medicine called lutetium Lu 177 dotatate (Lutathera). You get this medicine through an IV. This drug attaches itself to part of the tumor cell, and the radiation from the drug damages the cell.

Most of the time, surgery will cure an insulinoma. There could be side effects or complications after surgery, including:

  • Bleeding
  • Infection
  • Pain
  • High blood sugar (diabetes) if your surgeon removed a large part of the pancreas
  • Pancreatic fistula
  • Low digestive enzymes

If your insulinoma is cancerous, complications may include:

  • Metastasis
  • Low blood sugar if the cancer has spread to the liver