Glucose Tolerance Test (GTT)

Glucose Tolerance Test: What to Expect and What the Results Mean

In Fertility by The Modern Belly0 Comments

If you’re anything like me, the first time you’ve heard about the glucose tolerance test (GTT) was probably in the context of pregnancy. Friends were telling me about this test they had to undergo to determine whether they are at risk for gestational diabetes, and I figured that this test will not be relevant for me for quite a while. After all, I needed to overcome the challenge of getting pregnant first.

It turned out I was wrong. When my doctor diagnosed PCOS, he recommended taking the glucose intolerance test to understand whether I suffer from Insulin Resistance (IR). While not all women with PCOS have insulin resistance, insulin resistance is considered one of the causes for PCOS, so it was important to uncover whether this was the cause in my case. Since insulin resistance can also lead to type 2 diabetes or pre-diabetes, finding out about it early on can also help prevent or delay the onset of the disease.

Preparing for the Glucose Tolerance Test

Since the test’s goal is to see how your body reacts to glucose, you want to make sure that the baseline is as normal as possible, so try to eat like you normally would several days before the test. You will then need to avoid eating and drinking for 8-12 hours before the test, and of course you will not be allowed to eat during the test either. I erred on the side of caution and fasted 12 hours, so by the time I got to my 9am appointment, I was starving. As I was walking over to the lab, all I could see were bakeries and restaurants…

What Happens During the Glucose Tolerance Test?

I was given the oral glucose tolerance test (OGTT), which is the most common GTT for those who are not pregnant (the test for pregnant women is also oral but the process is somewhat different). The first step in the test is to take your blood sample to get a baseline of your fasting insulin levels. You are then given a sugary drink containing between 50-100 grams of glucose. Glucose Tolerance Test (GTT)I was handed a chilled drink that tasted like a very sweet, low-quality lemon-flavored soft drink. It had 500 ml of liquid and 75 grams of glucose in it, which is the typical amount of glucose used in these tests. In case you were wondering, 75 grams of glucose is equal to 19 teaspoons of sugar and 300 calories. You need to drink the whole thing in five minutes, and after two minutes I already downed two thirds. At that point I was quite sugared out, so I drank the remainder more slowly and agreed with myself that this will not become my drink of choice going forward. All in all, though, the drink wasn’t as disgusting as I expected it to be, and I didn’t feel too nauseated or lightheaded (which some people complain about). That is when the waiting begins – for the next 2-3 hours, a blood sample will be taken from you every 30-60 minutes to see how efficiently your body processes all that sugar. In my case, the test lasted two hours and the nurse took my blood samples 60 minutes and 120 minutes after drinking the liquid. I watched a lot of Netflix on my tablet in between. After my blood was drawn for the last time, I could finally go home and eat something, but I was no longer hungry – after ingesting so much sugar, I just didn’t feel like having anything for a few more hours.

Interpreting the Gluten Tolerance Test Results

According to the National Institute of Health, the normal blood values for a 75-gram oral glucose tolerance test for non-pregnant females are between 60-100 milligrams of glucose per deciliter of blood plasma (mg/dL) in fasting. One hour after drinking the glucose drink, your glucose levels should be below 200 mg/dL, and within two hours they should be less than 140 mg/dL. If after two hours, your glucose level is between 140-200 mg/dL, you may have impaired glucose tolerance, or pre-diabetes. If your two-hour glucose level is above 200 mg/dL, you might already have diabetes.

You Were Diagnosed with Insulin Resistance – Now What?

Insulin resistance is not the kind of doomsday diagnosis we all fear. The good news is that physical activity, healthy lifestyle and weight loss can help the body process insulin better. Women who are diagnosed with both PCOS and insulin resistance are often prescribed Metformin, an anti-diabetic drug that often helps regulate their cycles and increase their likelihood of getting pregnant. As many as 70% of women with PCOS are insulin resistant, so if you know or suspect you have PCOS, I highly recommend taking the Glucose Tolerance Test early on in your fertility journey. While I ended up being in the 30% whose PCOS is not IR-related, I’m still glad I took the test. After all, it is a relatively minor inconvenience that could have a significant impact on your fertility treatment plan.


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