Glucose Tolerance Test, what is it?

Diagnose Diabetes

Do you suspect that you might be diabetic?

Have a look at our list of common Diabetes symptoms to see if you may be a candidate.

Here is an abbreviated list…

  • Increased Thirst and Hunger
  • Frequent Urination
  • Dry mouth and itchy skin.
  • Blurred vision
  • Yeast infections
  • Slow-healing sores or cuts
  • Pain or numbness in your feet or legs

Fortunately, you don’t need to wait until you can see your doctor to get a reasonably good indication if you are diabetic.  You can run some simple tests at home.  This guide will walk you through the testing process.

Step #1 Understand What We are Testing and Why

We’re going to take some fairly simple blood glucose tests. There are 3 different Diabetes related conditions:

  • Type 1 (5-10% usually discovered in childhood)
  • Type 2 (90-95% discovered during adulthood)
  • Gestational Diabetes (pregnancy)

The tests for diabetes are conceptually quite simple. Diabetes is a condition where the body doesn’t regulate the amount of glucose in the blood properly. (Insulin is released by the Pancreas to manage blood glucose and diabetics typically have insufficient insulin production.)  So in order for Doctors to test for this, they check your levels before and after eating to see how your body is managing it’s glucose.

This test is known as a oral glucose tolerance test (OGTT). If you have this test done by a doctor typically they’ll have you fast (not ingest any calories) for 8 hours prior to the test to get a base level number. Then you’ll ingest some sugar (glucose) and they’ll run tests for the following 2 hours to see how much glucose remains in your blood stream.

You can do these tests at home, they’re quite simple.

Since you’re testing yourself and the strips are relatively cheap, there’s little harm in running through the whole suite of tests to get some solid data. The hardest part of this process is fasting for 8 hours, and if you already have to do that, you might as well collect as much information as you can.

Step #2 Buy a Blood Glucose Monitor

You’ll obviously need to get a blood glucose monitor. Don’t borrow your friend’s or family member’s. There have been two many incidences of cross contamination, so none of them are rated for sharing anymore.  Plus they’re cheap enough that you should get your own. Monitors are around $20USD and about $1 per testing strip.  For many people it’s probably cheaper than the insurance co-pay. If you’re an avid Autonomous Medicine reader you’ll probably find that you’re going to be using the monitor a fair bit to gather other personal data as well, so it wouldn’t hurt to spend a bit more to get a good one with useful features.

Shopping List:

  1. Blood Glucose Monitor
  2. Testing Strips
  3. 75 grams glucose solution (100 grams if pregnant)

Step #3 Fasting Glucose Test

So we need to monitor how much glucose is in your blood after a period of at least 8 hours of fasting. It’s VERY important that you not eat anything during this time, as it will skew the results.

The easiest way to do this is to take your blood glucose measurement in the early morning at least 2 hours before you have breakfast.  During this late night fast, you can only drink water, nothing else.

**You’re going to be waking up early in the morning and probably not very coherent, so it would be wise to run through a sample test or two to make sure you know how to use your monitor before attempting to do it in the morning. Tests are mildly time sensitive, so it would be better if you don’t have to spend 30 minutes trying to figure out how to use the equipment as that will through all the timetables off.

Go to bed early and set a series of alarms:

  • 1st Alarm –  2 hours before you normally get up
  • 2nd Alarm – 1 hour before you normally get up
  • 3rd Alarm – your normal wake up alarm

** If you’re pregnant you’re going to need to drink 100g of glucose solution and take one extra measurement, so you’ll want to add one more alarm, so start your alarms 3 hours before you usually wake up.

For example, I usually wake up at 8am:

  • 1st Alarm – 6am
  • 2nd Alarm – 7am
  • 3rd Alarm – 8am (normal wakeup alarm)

NO SNOOZING!!  Anyway for the first two you can go right back to sleep.

The Routine

 ** be sure NOT TO EAT or DRINK ANYTHING except the glucose solution and water (until you’ve completed all 3 tests)  

1st Alarm

Wake up and take your blood glucose measurement.
Drink a 75-gram solution of glucose.

2nd Alarm

Take your blood glucose measurement.

3rd Alarm

  Take your blood glucose measurement.

4th Alarm (pregnant women only)

Take your blood glucose measurement.

Congratulations, you’re done! ^_^
Eat your well-deserved breakfast and check your results.

Step #4 Check Results

Fasting (1st test)

Pre Diabetes 100-125 mg/dL
Diabetes > 126 mg/dL
Gestational greater than 95 mg/dL

1 Hour

Diabetes > 184 mg /dL
Gestational > 180 mg/dL

2 Hour

Pre-Diabetes 140-199 mg /dL
Diabetes 200 mg / dL
Gestational > 155 mg /dL

3 Hour (gestational test only)

Gestational > 140 mg /dL

Gestational Diabetes:

If 2 of the 4 readings are in the Gestational Diabetes Range, then you are likely to be diagnosed with gestational diabetes. Which is quite a serious condition if left untreated, so if you’re testing positive, or even borderline, you should see a doctor and start treatment as soon as possible.

If your numbers are borderline, because there are variations in blood glucose levels throughout the day, it would be advised to take a second battery of the same tests at a different time of the day.

Probably the easiest thing to do is to eat a hearty breakfast and skip lunch, then do your 2 hours of testing after work and before dinner. This is a bit trickier because you have to abstain from food and drinks all day after breakfast. Ensure that there is at least an 8-hour gap between any calories and your tests. Don’t forget that sugary drinks and coffee with milk/sugar have calories as well, so you need to avoid those too.


If your numbers are indicative of Diabetes, don’t fret, there is a lot you can do to control it.  However, this is a VERY SERIOUS condition and needs to be dealt with immediately.  The first thing you should do is schedule an appointment with your doctor.

Obesity is the #1 cause of Type 2 diabetes, if you’re overweight then you already know what you need to do.

Diabetes management is really inconvenient and not desirable at all.  Cleaning up your lifestyle a bit, is considerably easier than having to deal with an insulin pump, or constantly checking your glucose levels and having to give yourself insulin injections.

It’s hard to know where to start, if you’ve got a long list of improvements.  In the short term, these 3 will get your the biggest.  You can and should refine these as you get more accustomed to your new lifestyle, but in the beginning if you can just incorporate these simple changes, you’ll see a dramatic impact.  Just be patient.

  1. Quit Smoking (Do this before trying to tackle any other aspect of your life)
  2. Get Moderate Exercise (Just go for a walk for 20-30 minutes a day, easy)
  3. Slow your roll when eating, try and cut your typical portions by 1/3.

Take a look at a list we’ve compiled of our most efficient lifestyle changes for the biggest health gains.  Low Effort, High Rewards, Big Wins.



What’s been your experience with self diabetes diagnosing?




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