Blood Sugar Testing 101….FINALLY, it all makes sense!

 blood glucose test

Why Test?

As a registered dietitian and certified diabetes educator, I’ve directed Diabetes Centers in hospitals, have a private practice in medical nutrition therapy and have written a NY Times Bestselling books on diet for weight reduction, metabolic syndrome, pre diabetes, and type 2 diabetes.  I have had type 2 diabetes for 15 years.

Guess what?  If you asked me what my blood sugar is right now, I have no idea.  Neither do you!

●Did you know that unless your blood sugar is over 200mg/dL, it is possible you will have none of the traditional diabetes symptoms such as excessive thirst, urination, fatigue, hunger, or wounds that will not heal?

● If your blood sugar has been  over 200mg/dL for a period of time, you might not even have symptoms when your sugar exceeds that 200mg/dL point.

● If you have been prescribed medication for diabetes that is aimed at reducing your blood sugar and you begin to feel shaky, dizzy, nauseated, can’t speak clearly, can’t think, feel wiped out….you may assume that you are hypoglycemic.   But, are you REALLY hypoglycemic?  Without testing, you really have no idea…your once high readings may have returned to normal range…and your body may assume you are hypoglycemic when you are far from it!   If you grab juice or glucose tabs, you will push your normal sugar right back into the very high range.

● Or maybe your symptoms  are hypoglycemia and if you don’t treat it, you will lose consciousness, fall down the stairs, drop your child, run off the road.

● Your Hemoglobin A1C might be 6.3 and you think to yourself:  “Wow, my blood sugar is now normal…why should I spend the money and take the time to test?”  Do you realize that hemoglobin A1C is your average blood sugar 24 hours/day, for about 3 months back in time?  An average is the average of highs and lows.  It is possible to have a 6.3 hemoglobin A1C because you are averaging normal from blood sugar readings that are in the high 200’s and in the low 50’s!

● You may be following your meal plan, exercising, are not stressed, haven’t been sick and think maybe you don’t need that medication.  Without monitoring, how can your physician make an educated decision on your medication or doses?

When Should I test?

ImageTesting your blood sugar is a quick, not overly painful, fairly accurate way to determine where your blood sugar stands at different times of the day.  Many people don’t know when they should test.   People with type 1 diabetes usually test before each meal, at bedtime, and anytime they feel low.  People with type 2 diabetes have a much different test schedule.

I can’t tell you the number of patients I’ve seen who only test first thing in the morning.  They initially come to my office with months of wake up (fasting) readings.  I scan them, see some high readings, and ask…What do you think caused your fasting reading to be so high on this morning or that one?

Invariably, the patient will “confess” one of the following scenarios:

– The night before, I went out to dinner late and ate pasta, garlic bread, and zeppoles. .

-The night before, I over-snacked watching a late night football game.

-I had a bagel for breakfast and a candy bar in the afternoon the day before.

-I had a snack right before bed

Well, here is an eye-opener.  When a person with type 2 diabetes has a high fasting blood sugar, it is usually not because of anything you ate the day or night before!!!!

Carbohydrate is the nutrient that converts 100% into blood sugar and has a lifespan of about 4-5 hours.  When more than 5 hours pass after you eat carbohydrate food, your  liver gets a signal to release glycogen (sugar stores) into the blood.  So…anytime you check your blood sugar and more than 5 hours have passed since you last ate, the blood sugar reading you see is from your liver’s self -feeding mechanism!

If you only test your blood sugar in the morning before you eat, you are only seeing what your liver released during the night when you were sleeping.  That reading tells you nothing about how your body is reacting to the food you ate the previous day/night.

So, how can you find out how you are handling food (specifically carbohydrates)?  You should consider testing your blood sugar 2 hours after the START of a meal.  So, if you are having dinner at 6 PM and want to assess how high your blood sugar rises from dinner, test at close to 8PM.  If you wait until bedtime at 11PM, you missed it….because you are at the 5 hour mark.  After you eat, your sugar rises for about 2 hours, then comes back to normal over the next 2 hours, then hangs tight for the last hour of the 5 hour blood sugar curve.

What two times of day can I see my blood sugar at its highest?  Check first thing in the morning before you eat (checks the liver) and 2 hours after the start of your largest meal (checks the impact of food).

  What Should My Readings Be?

The following are the blood sugar ranges I typically use with my patients with type 2 diabetes whether they are following diet plus exercise or diet, exercise plus oral meds:

Fasting:  blood sugar less than 120mg/dL  (80-120mg/dL). A person with no diabetes will have fasting blood sugar 100 or less.  A person with pre diabetes will have fasting blood sugar 110 or less.

2 hours after the start of a meal:  blood sugar less than 140mg/dL.  If you happen to miss the 2 hour after time and check at 3 hours it should be under 130mg/dL.  If you don’t check until 4 -5 hours after the start of a meal it should be under 120mg/dL.  You can see that the highpoint is at the 2 hour mark.

Those with type 2 diabetes taking insulin will usually test premeal and at bedtime.  Your MD will tell you your individual targets if you use insulin to control your diabetes.

Woman holding glucometer and writing in blood glucose log.

What Do I Do with My Readings?

I find it is helpful to keep a written record of my blood glucose readings.    Your blood glucose meter can keep hundreds of readings in memory with a time stamp (if you bother to set the meter’s time) but for me….I like to see patterns.  Even if you only use a sheet of paper…you can head it like this and mark or circle your readings that are out of zone.  Then, try to come up with a reason.

Fasting        after breakfast                after lunch                     after dinner                   Reason

110                 2hrs= 126

107                                                        2 hrs = 157*                                                        *Bagel 

140*                                                                                                 2 hrs = 122               *Bad sleep

152*                 3 hrs = 120                                                                                              *Poor sleep

139*                                                                                          2 hrs = 109                       *Bad sleep

By highlighting any numbers that are out of range and trying to come up with a reason for the reading, I can see that my sleep difficulties are really affecting my fasting blood sugar and may need to address this with my MD if the situation does not improve.

 Why would my fasting reading be elevated?

  1. Poor sleep
  2. Pain
  3. Infection or Illness
  4. Not eating a night snack (liver is “on” longer)
  5. No exercise previous evening (muscles “consume” blood sugar for hours after exercise ends)
  6. Forgot to take my Metformin at bedtime
  7. Right before menstrual period
  8. Stressed out

Why would my post meal readings be elevated?

  1. Forgot my medication today
  2. Pain
  3. Illness or infection
  4. Overeating carbs at the meal I’m checking
  5. No exercise earlier in the day
  6. Right before menstrual period
  7. Taking steroid based medication (prednisone/cortisone)
  8. High stress day

What about low blood sugar?

Low blood sugar under 70mg/dL, when taking diabetes medication (orals or insulin),  is considered to be hypoglycemia and needs to be treated as directed by your physician.

The standard treatment is a quick source of carb like 3-4 glucose tabs, ½ cup juice, ½ can regular soda (6 ounces), 8 ounces nonfat milk, 1/2 cup regular Jello. After waiting 10 minutes, retest your blood sugar and make sure the reading is over 80.  If your blood sugar remains under 80 after the treatment, repeat and retest in 15 minutes to make sure your reading is  over 80.  Report repeated hypoglycemia (not an isolated event) to your physician as you may require a medication or dosage change.

More About The Metabolism Miracle, The Diabetes Miracle,  and Diane Kress!  

Diane Kress is the author of the New York Times Bestseller;

The Metabolism Miracle:

The Metabolism Miracle Update:

The Metabolism Miracle Cookbook:

The Diabetes Miracle:  The interactive online support group for all Diane Kress’ Miracle programs is at

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About Diane Kress

Author of The New York Times Bestseller; The Metabolism Miracle, The Metabolism Miracle Cookbook, and The Diabetes Miracle. and The Metabolism Miracle, Revised Edition. Owner, developer, and administrator of The Metabolism Miracle's support site: Registered Dietitian, Certified Diabetes Educator, Email:
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