People using the MMTT drink a liquid meal of mixed proteins, carbohydrates, and fats. Their blood samples then are evaluated to see how much insulin—a key hormone that helps your body use blood sugar—rises in response.
This article explains how the MMTT works, from beginning to end of the test process. It also discusses the general importance of screening for diabetes.
Uses of MMTT
The MMTT is most often used as a tool in research settings, such as clinical research trials. You’ll rarely encounter the complex and time-consuming MMTT when seeing your healthcare providers, but sometimes it’s used to evaluate people with type 1 diabetes.
That said, there are specific contexts for when the MMTT is used to evaluate people living with diabetes. The test results can show whether the pancreas is producing too much insulin, not enough, or no insulin at all.
Healthcare providers encounter a number of scenarios in which the test may offer benefits. You may see the MMTT used when:
A very young child is diagnosed with type 1 diabetes and the provider needs to know how much insulin their pancreas is still making A person has episodes of post-meal hypoglycemia, or low blood sugar, after having gastric bypass surgery Someone doesn’t have diabetes but their blood sugars are low two to three hours after eating; an MMTT can help to identify reactive hypoglycemia and determine if the pancreas is releasing excess insulin in response to food A person with a suspected insulinoma (a tumor of the pancreas) has recurrent episodes of hypoglycemia
There also is some evidence for using an MMTT to evaluate people with type 2 diabetes.
The MMTT and What to Expect
Before completing an MMTT, you will first need to avoid all food and drink for at least eight hours beforehand. This is called fasting and means you’ll take in nothing other than water. Even a breath mint or chewing gum that contains sugar can throw off the results.
You also may be asked to limit certain activities a day before the MMTT because they can influence insulin sensitivity. These activities include:
Strenuous exercise Drinking alcohol Using caffeine Smoking or chewing tobacco
Expect to stay for several hours during the test. Once an intravenous (IV) line is started and you drink the MMTT beverage, your blood will be drawn every 30 minutes for at least two hours.
Some research has supported a shorter MMTT test of just 90 minutes with only one blood draw.
MMTT v. Oral Glucose Tolerance Test
The oral glucose tolerance test (OGTT) is another method used to test people living with diabetes. It is a good indicator of glucose tolerance and is used with other tests, such as the hemoglobin A1C. It’s similar to the MMTT and used for much the same purpose, but there are differences.
The OGTT is used to diagnose diabetes and prediabetes, a condition in which you have mildly high blood sugar levels that may progress if not treated. The OGTT also may be used to screen for gestational diabetes, which happens only during pregnancy.
The biggest difference between the MMTT and the OGTT is that people taking the OGTT don’t ingest an entire mixed meal. With this test, you’ll take in only sugar dissolved in water, and then your blood sugar levels will be checked later.
Your healthcare provider can use the OGTT to test for things the MMTT cannot. This includes two measures: impaired fasting glucose (IFG) and impaired glucose intolerance (IGT), both associated with prediabetes.
Other Tests Used to Screen for Diabetes
There are several other tests that may be used to evaluate diabetes. Here are a few and the reasons why they’re ordered.
Hemoglobin A1C Test
The hemoglobin A1C test is used to measure the percentage of your blood cells that have sugar attached to them. That’s because people with diabetes will have more sugar attached to their blood cells than others do. The simple blood test shows average blood sugars over a three-month period.
Fasting Blood Glucose Test
A fasting plasma glucose (FBG) is a simple and easy test to check your blood sugar level after you’ve not eaten for at least eight hours. A blood sample is taken to see how much glucose remains in the bloodstream. Along with the random blood glucose test (which doesn’t require fasting beforehand), it’s a typical test used for initial screening for diabetes.
Fructosamine Test
The fructosamine test may be used instead of the A1C in certain groups of people, including those with sickle cell anemia and people living with HIV. It measures how much sugar sticks to proteins in the blood, in order to know the average blood sugar levels you’ve had in the last two to three weeks.
Autoantibodies Test
People with a family history of diabetes may be more likely to develop type 1 diabetes. Newer tests are designed to identify autoantibodies that have been linked with diabetes.
The body makes antibodies to protect itself against infection and other threats, but sometimes it will turn on itself. This is the underlying cause of many autoimmune disorders. The autoantibodies involved with diabetes include those that attack insulin and the islet cells of the pancreas.
When present, they may be able to predict the development of type 1 diabetes years in advance.
Summary
The mixed meal tolerance test is used to measure how well certain insulin-producing cells in your pancreas, called beta cells, are working. For an MMTT, you’ll drink a mixture of sugars, proteins, and carbohydrates, and then have your blood tested several times to see how well your body responds.
Many other types of diabetes tests are available, so the MMTT is most often used in research settings. But it is used in a few clinical scenarios.
A Word From Verywell
Don’t hesitate to get tested for diabetes if you or a loved one experience increased thirst, increased urination, or other common symptoms of diabetes. Your healthcare provider can order the test for you and, if necessary, start you on a treatment plan.
