Am I Diabetic? How to Test Your Own Blood Sugar To Find Out

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Am I Diabetic? How to Test Your Blood Sugar To Find Out
If you have not been diagnosed with diabetes but suspect you might have something wrong with your blood sugar, there is a simple way to find out.

What you need to do is to test your blood sugar after you have eaten a meal that contains about sixty grams of carbohydrates.

You can ask your doctor to test your blood sugar in the office if you have an appointment that takes place an hour or two after you've eaten or, if this isn't an option, you can use an inexpensive blood sugar meter to test your post-meal blood sugar yourself at home.

You do not need a prescription to buy the meter or strips. One advantage of testing yourself at home is that with self-testing you do not run the risk of having a "diabetes" diagnosis written into your medical records which might make it impossible for you to buy health or life insurance.

To run a post-meal blood sugar test do following:

  1. Borrow a family member's meter or buy an inexpensive meter and strips at the drug store or Wal-Mart. The Wal-mart Relion meter store brand meters sold at pharamcies like CVS, Walgreens, etc are usually the least expensive.

    Some meters come with 10 free strips. Check to see if the meter you have bought includes strips. If it doesn't, buy the smallest package size available. Strips do not keep for very long once opened, so don't buy more than you need for a couple tests. If you have access to a One Touch Mini or older One Touch Ultra meter that allows the strip code to be set, instead of buying the very expensive One Touch strips, you can buy equally accurate but much cheaper Genstrip Test Strips from Amazon.
  2. Familiarize yourself with the instructions that came with your meter so that you know how to run a blood test. Practice a few times before you run your official test. Each meter is different. Be sure you understand how yours works.

  3. The first thing in the morning after you wake up but before you have eaten anything, test your blood sugar. Write down the result. This is your "fasting blood sugar."
  4. Now eat something containing at 60 - 70 grams of fast acting carbohydrate. A bagel makes a good test food. If you can't eat wheat, a large (8 oz) boiled potato of a cup of cooked white rice will do. Avoid eating fats along with your test food as they can slow down the action of the carbohydrate.
  5. One hour after you started eating, test your blood sugar with the meter. Write down the result. If you lose track of the time measure as soon as possible. The numbers will still be useful.

  6. Two hours after you started eating test your blood sugar again. Write down the result.
  7. Three hours after you started eating, test your blood sugar. Write down the result. You are now done and can eat whatever you want.

What Your Meal Test Numbers Mean

Understand Your Meter's Margin of Error

Your meter is not as accurate as a lab-drawn test would be. Figure in a 10% error, plus or minus. So if you got a 100, your results might actually be 90 to 110 if you were tested at a lab. The documentation with your meter might tell you that it is only accurate to within 20%, however, in practice most meters nowadays are more accurate than this.

NOTE: All blood sugar levels discussed on these pages refer to plasma calibrated meter readings which are the kind of readings you will get from all meters now sold in the US. Some meters sold elsewhere in the world, especially in the UK, still use a different calibration. These are "blood calibrated" meters. If you are using one of these, you should divide the numbers given here by 1.12 to get the blood calibrated equivalents.

A Special Consideration if You Have Been Eating A Low Carb Diet

If you are currently eating a low carb diet--especially a diet that provies less than 75 g of carbohydrate a day, your post-meal test result will be slightly higher than it would be if you were eating over 150 grams of carbs a day. That is why, if you were going in for an official post-meal test or a glucose tolerance test ordered by your doctor, you would be told that you have to eat 150 grams of carbohydrate during 3 days before your test to get a valid result. However, since this is an informal test you probably don't want to stop your diet for that long. So when you get your result, you can make an informal adjustment to your post-meal test results that will account for the fact that low carbing temporarily raises your post-meal values when you eat an unaccustomed large dose of carbohydrate.

To make this correction, just subtract 10 mg/dl from any post-meal result that is over 140 mg/dl at 2 hours if you are currently low carbing. This is a very rough estimate, but close enough for this kind of home testing.

Interpret your result

Normal Blood Sugar

If your blood sugar reading remained under 100 mg/dl (5.6 mmol/L) at the one hour test and all the later tests, you have completely normal blood sugar and can stop worrying about it.

If your blood sugar did not reach 140 mg/dl (7.7 mmol/L) an hour after taking a large dose of carbohydrates and if it was below 120 mg/dl (6.7 mmol/L) two hours after you ate the large dose of carbohydrate, most health authorities would also say that you are normal. These numbers, 140 mg/dl at 1 hour and 120 mg/dl at two hours after a meal are what Joslin Diabetes Clinic of Harvard Medical School defines as upward limit of "normal."

You can see more data about what normal blood sugar levels look like here: What is a Normal Blood Sugar?

If your blood sugar is at the very top of this normal range, near 140 mg/dl (7.7 mmol/L) and near 120 mg/dl at two hours, you may have a very slight amount of either beta cell dysfunction or insulin resistance going on. If you are at the high end of the normal range, especially if you are noticing that you are gaining weight more easily than you used to, it might be a good idea to cut back on the amount of carbohydrate you eat and begin an exercise program.

Impaired Glucose Tolerance

If your blood sugar surged over 140 mg/dl at one hour or stayed above 120 mg/dl at two hours, you may have what doctors will call "impaired glucose tolerance" or IGT. Another name for this condition is "pre-diabetes." Note that the values given here are lower than the values doctors used to diagnose impaired glucose tolerance using a lab glucose tolerance test. That is because blood sugar does not rise as high after you eat a food that needs to be digested as it does when you drink pure glucose so you will not see as high a number with a food test as you will on a glucose tolerance test.

If your blood sugar stays above 140 mg/dl two hours after eating, you are definitely pre-diabetic using the criteria set by the American Diabetes Association.

If you suspect that you have impaired glucose tolerance, don't ignore it. The excess glucose molecules that make up those elevated post-meal blood sugars will bond to your body proteins, deposit themselves in your arteries, damage your kidney filtration units, clog up your retinal capillaries, and cause your nerve function to deteriorate leading to, among other things, impotence and pain. Keep this up, and in another five or ten years you'll be one of those people with "newly diagnosed" diabetes who have serious, established, possibly irreversible long-term complications.

On a more cheerful note, if you catch your blood sugar abnormality at this point, there is a very good chance that by managing your blood sugar through cutting down on how much carbohydrate you eat and adding exercise, you may never see it deteriorate further and may avoid developing any diabetic (or pre-diabetic) complications.

A helpful strategy that uses your blood sugar meter to show you what to eat to get back to normal blood sugars is discussed here:
How to Lower Your Blood Sugar

If you discover you have impaired glucose tolerance, be sure to discuss this finding with your doctor. If he or she tells you it is "nothing to worry about" it's time to find another doctor-- one who is more up-to-date and who will help you manage your blood sugar so you can avoid heart disease and development of other complications that have been linked to pre-diabetic blood sugars.

Studies have shown that people with impaired glucose tolerance who lose weight and start exercising can reverse their blood sugar deterioration and prevent themselves from progressing to full-fledged diabetes. There are also drugs that can help you, too. And the very best treatment is lowering your carbohydrate intake.

But if you wait for a diabetes diagnosis before taking action, it is often too late. By the time your fasting blood sugar has reached 126 mg/dl (7.0 mmol/L) (the level at which most doctors will diagnose you) at least half of your beta cells may be dead and they may not be able to regenerate.

This page will tell you more about: The Patterns in Which Diabetes Develops.


If your blood sugar went over 200 mg/dl (11.1 mmol/L) at any time you tested, you just registered a diabetic blood sugar level and should consult with a doctor as soon as possible. Two random tests results of 200 mg/dl are considered diagnostic of diabetes according to the Diagnostic Criteria for Diabetes Mellitus published by the highly conservative American Diabetes Association.

Again, if your doctor says, "Let's just check it again in a couple months" and does not urge you to take a more aggressive approach, it's time to look for a new doctor, one who has kept up with the current approaches to managing diabetes. It's your kidneys, heart, nerves, and vision that are at risk, not his. A doctor who is supportive of your desire to reclaim your health will prescribe a meter for you (which will get your health insurance to pay for the meter and strips.) This will allow you to use the single most effective treatment for lowering blood sugar, which you will find here:

How to Lower Your Blood Sugar.

Low Blood Sugar

If your blood sugar goes up at one hour and then drops below 70 mg/dl (3.9 mmol/L)at the two hour point you have what is called "reactive hypoglycemia." What happened was this. After you ate all those carbs, your blood sugar went up but your body cranked out a huge dose of insulin to bring it back down--too much, in fact. That high dose of insulin resulted in your ending up with low blood sugar.

This, too, may be an early warning sign that you might be headed for diabetes, though it may take a decade or more until it becomes apparent. Even if you don't progress to diabetes, reactive hypoglycemia may be a sign that you are insulin resistant and that your cell's resistance to insulin is forcing your body to secrete the very large insulin doses that are driving your blood sugar low. Insulin resistance, with or without diabetes, may be a precursor to heart disease. Be sure to discuss this result with your doctor.

Though you may have been told that eating protein meals is a good way to control hypoglycemia, a better way is to cut back on the carbohydrates you eat, as it is carbohydrates that cause the spike in insulin that drops your blood sugar too low.

After You Have Tested

Once you have done this "baseline" post-meal blood sugar test if what you saw was anything but rock solid normal, every three months you should test your blood sugar response at home using same the test food you used for your first blood sugar test to see how your blood sugar control is progressing. The values you get on a meal test may fluctuate by as much as 30 mg/dl (1.7 mmol/L) from what you saw on a previous meal test. But if you see your blood sugar registering test values that are steadily going up, test after test, it is time to talk to your doctor.

If you have abnormal post-meal tests, ask your doctor run an Hba1c test at least once a year and have him tell you the number you got on the test. Ignore whether or not your test meets the the lab definition of "diabetic" which is MUCH too high. Instead track instead whether your A1c test result is staying the same or rising. If your hba1c goes over 5.7%.which many endocrinologists consider to be the level at which diabetes becomes a possibility, it's time to get serious about lowering your blood sugar. Try the strategy discussed on the How To Lower Your Blood Sugar flyer. If that doesn't work, it's time to read up on oral diabetes drugs and work with your doctor to find the solution that works best for you.

Most people with mild blood sugar abnormalities can attain completely normal blood sugars through cutting out excess carbohydrates from their diets, especially fast-acting ones like those in soda, candy, cake, white flour, and in starchy vegetables like potatoes.

Use your meter to determine how much carbohydrate you can eat without causing a blood sugar spike. Ideally you would want your blood sugar to drop below 100 mg/dl an hour after eating (or sooner) and then to stabilize somewhere between 70 mg/dl (3.8 mmol/L) and 90 mg/dl (5 mmol/L). Remember that the lower your post-meal blood sugar, the lower your risk for heart attack and the other "diabetic" complications that research has found actually start when blood sugars rise into the "pre-diabetic" range.

