diabetes management lecture 4

Blood Glucose Monitoring (You Can’t Achieve Tight Control Without It)

Lecture 4

by Eric Holzman

A Diabetic’s Guide to Managing Diabetes

by Eric Holzman9-18-07 2

Without blood glucose testing, a diabetic is “blind”

• A normal person’s blood glucose control system does not need external adjustment because his body

– continuously monitors his blood glucose level

– releases insulin or glucagon

– stores or releases glucose

• A diabetic’s blood glucose control system requires external adjustment.

– Insulin and/or Medication

– Food

– Blood glucose testing to determine what to do

• A diabetic who knows his blood glucose level can decide whether he needs to do nothing, take medication, exercise or eat food.

Type 2

Type 1



Blood glucose level—what does the number mean?

• Successful diabetes management aims for a normal blood glucose level all day, every day.

Do nothingNormal80-100

Exercise or take insulin

Above normal100-120

Take insulinHyperglycemic (high blood glucose)

Above 120

Eat food with up to 5 grams carbohydrate

Below normal60-80

Eat food with 5-10 grams fast acting carbohydrate

Hypoglycemic (low blood glucose)

Below 60

What a diabetic should do

What it meansBlood Glucose Level (mg/dL)

goal



Can you know what your blood glucose level is without measuring it?

• If your blood glucose level is high (above 100 mg/dL), it’s doubtful that you will be able to tell how high.

– I have no symptoms if I’m within or above my normal range (80-100 mg/dL).

• Hypoglycemia (60 mg/dL or lower) may be indicated by symptoms.– Disorientation, lethargy, fatigued limbs, shakes, numbness, nausea

• Low blood glucose is a relative term: you may experience hypoglycemic symptoms if your blood glucose level drops significantly below its “usual”range.

– When I was diagnosed, my blood glucose level was 300-400 mg/dL.

– I implemented carb-reducing changes in my diet immediately.

– I experienced low blood glucose symptoms such as “shakes” as my blood glucose fell from 300-400 to 200-300 mg/dL in a few days.

• Hypoglycemic unawareness is a major reason why testing is necessary for insulin users.

– If my blood glucose level drops to 50 mg/dL several times over a period of a few days, many symptoms go away—sometimes I feel almost normal.



How frequently should you measure your blood glucose level?

• How often you should test depends on

– how stable your blood glucose level is throughout the day,

– Your ability to predict changes in your blood glucose level,

– the chance you might have a hypoglycemic reaction,

– how tight you want to control your blood glucose level.

• Tight control means more frequent testing.

– In a normal person, continuous monitoring is done by the pancreas.

– A diabetic on insulin tests

• before eating to determine how much insulin to take, and

• after eating to determine whether the dose was correct

6:30 AM 78 12:00 PM 77 6:00 PM 79 8:30 PM 97Breakfast 3.5 units Lunch 6 units Dinner 2.5 units snack 3 units

8:30 AM 102 2:00 PM 97 Bike for 22 minutes 10:30 PM 79

7:00 AM 94 12:30 PM 72 6:00 PM 77 9:00 PM 109Breakfast 4 units Lunch 4.5 units Dinner 4.5 units snack 3.5 unitswork outside 3:00 PM 63 8:00 PM 125 10:30 PM 113

9:00 AM 49

Good day8/30/06

Bad day9/10/06



When do you test and why?

• Fasting—before eating

– A type 1 diabetic must know his blood glucose level to choose his insulin dose.

– Your fasting level tells you if your slow acting (basal) insulin dose requires adjustment.

• Post prandial—after eating provides important feedback

– Did you take the correct amount of medication?

– Did you eat too much?

– Did you over-exercise?

• Post prandial measurements should be made about two hours after eating.

– Your meals should be sized to digest in about two hours because

– fast acting insulin (Lispro and Aspart) operates for about two hours.

– If you overeat,

• Digestion will take longer than two hours, and

• you may need to re-test after another hour.

• Testing at bed-time is essential for insulin users.

• You should test any time you think your blood glucose is too low.

2:00 PM 71Lunch 5.5 units

4:30 PM 1006:00 PM 130



70

80

90

100

110

120

6:00 AM 10:00 AM 2:00 PM 6:00 PM 10:00 PM

Time of day

Blo

od g

luco

se le

vel

7 tests/day4 tests/day

Breakfast

Lunch

Dinner

Snack

Frequent testing enables you to reduce your blood glucose level

• If you do not test after eating, your blood glucose level could remain high until the next meal.

• Your bedtime test is the most important—your life may depend on it.

– Not testing at bedtime could mean disaster if your blood glucose level is low.

– A high blood glucose at bedtime means a whole night at the wrong level.

– Your bedtime and morning fasting tests give you essential feedback for setting your long-acting insulin dose properly.

Testing more often means a lower average blood glucose level



Portable blood glucose measurement equipment is essential for tight control

• A glucometer is a device that measures your blood glucose level.

• The test requires a spring-loaded lancing device and lancet to draw a small drop of blood from your figure or arm.

• The blood sample is absorbed by a test strip, which is inserted the glucometer.



How to choose a Glucometer—Accuracy and precision matter the most

• Accuracy: correctness, degree of conformity of a measure to a standard or true value.

• Precision: repeated measurements produce the same results.

• American Diabetes Association recommends accuracy goals to metermanufacturers.

– < 10% for blood glucose levels between 30 mg/dL and 400 mg/dL

– Example: 90 mg/dL could really be anything from 81 mg/dL to 99 mg/dL

• A laboratory meter is the standard.

• Cardiovascular system carries blood throughout the body to feed our cells.

– Arteries carry blood from heart to smaller arteries, which carry blood to capillaries.

– Glucose and oxygen leave capillary blood to supply cells. Cells return waste.

– Capillaries deliver blood carrying waste to veins, which return blood to heart.

V. Peragallo-Dittko, “How Accurate is Your Meter,” Diabetes Self-Management, 9/10 2000.



How to choose a Glucometer—why lab and glucometer tests may not agree

• Blood in capillaries has more glucose than that flowing in veins.

– After fasting, the difference is small.

– After eating, the difference is large.

• Laboratory samples are from veins, while glucometers measure glucose in capillary blood.

– For closest comparison of lab and glucometer measurements, lab samples should be taken during fasting periods.

• Laboratories measure glucose level of plasma, the fluid in blood, while some meters measure glucose level of whole blood (plasma and red blood cells).

– Measurements of whole blood are 10% to 15% lower than of plasma only.

• Most meters provide an average of 100 or more readings, which should compare well with the result of an HbA1c test.

V. Peragallo-Dittko, “How Accurate is Your Meter,” Diabetes Self-Management, 9/10 2000.



How to choose a Glucometer—other features that make your life easier

• Small blood sample—mine takes 2.5 microliters of blood.

• No coded entry for each new batch of strips reduces chance of error.

• Quick analysis time: 15 seconds or less.

• Storage of 100+ readings and calculation of long term averages.

– Averages tend to be very accurate—should compare with HbA1c.

– Take an even mix of pre and post-prandial readings.

• Too many fasting readings may bias the average to the low side.

• Too many post-prandial readings may bias it high.

• January Issue of Diabetes Forecast Magazine lists latest equipment from all manufacturers.

This is a small sample: a few microliters



How to choose a glucometer—the most overrated feature

• Some glucometers can transfer stored results to a computer.

• By themselves, the readings don’t tell you that much.

– Many things determine your blood glucose level at any one time: time of day, activity level, medication dosage, when, what & how much you last ate,…

– Unless you transfer all these additional data to your PC, plotting blood glucose readings by themselves will not be useful.

• Your test results should be kept as part of a written record containing your food intake, medication dosage and level of physical activity.

• I write all my data in small book, with 7 days of records viewable at a glance, so I can see the trends.

Use thisinstead of this



Testing--a small amount of preparation means accuracy and consistency

• Wash your hands with soap prior to testing.

– I always wash my hands in the bathroom.

– Not near a washroom? Carry some small towlettes with you.

• Dry your hands with a clean towel or a paper towel—not a kitchen towel, which might have food residue on it.

• It is easiest to get a blood sample from warm hands.

– If your hands are cold, shake your fingers towards the floor to get the blood flowing to your fingertips.

Bernstein, pp. 69-72



Measuring your blood glucose level is quick, easy and almost painless

• Lance your finger from the side for minimum pain.

• You may need to squeeze your finger to get a large enough blood sample.

• Switch fingers for your next test.

• Try to apply the blood sample to the strip as quickly as possible without rushing.

• If the sample is too small (it does not fill the strip), ignore the reading, and start again with a new strip.

• Often, you must insert the strip into the meter beforeapplying the blood sample to the strip.



You should question your glucometer’sresult if it is not what you expect

• Even a glucometer that works perfectly can give an inaccurate reading.

– Some meters require a code for each batch of strips—make sure the correct code is in use.

• A false high reading can cause you to take medication and lead to a hypoglycemic reaction.

• What should you do? Test a 2nd time from a different site.

– If the 2nd reading differs greatly from the 1st (>10 points difference), wash your hands and test a 3rd time.

– Usually, 2 of the 3 readings will be in close agreement. Average the closest two readings.



Sore Fingers--what about other test sites?

• Other test sites generally do not give real-time results like fingers (see Roche glucometer manual).

• Evaluate a new site by comparing it with a result from a finger stick taken at the same time.

– Take two readings, one from your finger and one from the new site.

– If the difference is greater than 5 points, retake both readings.

– You want to see a majority of readings at each site in close agreement.

• For example, you want to test from your arm instead of your fingers.

– Since the two readings at each site are close, you can conclude, that the roughly 20 point difference is due to the site choice.

90

110

TEST 1 87

105

TEST 2



The A1C test: a diabetic’s report card

• The glycosylated hemoglobin (HbA1c) test gives an indication of “average” blood glucose control over previous 2-3 months.

– fasting not required

• Red blood cells allow glucose to freely enter and leave without aid of insulin.

– Concentration of glucose inside a red blood cell is the same as that in the blood.

• Hemoglobin: a molecule found in red blood cells.

– Carries oxygen from lungs to body’s cells.

– Variety of types; HbA1c is the type that interests diabetics.

– HbA1c joins with glucose (is glycosylated) for the life of the blood cell, about 4 months.

• This test measures the % of hemoglobin HbA1c molecules that are glycosylated.

• Since your blood contains a mix of blood cells of different ages, blood cells aged 0-4 months contribute to the test result.

– 50% determined by blood glucose levels in the month before the test.

• Take an A1C test at least twice a year.

• Result is a percentage—5% is normal: 1 out of 20 hemoglobin are glycosylated.

M. Nakamoto, “H-B-A-1-C (what it is and why it matters),” Diabetes Self-Management, Jan/Feb 2004, pp. 84-89.



Relating A1C test results to your glucometer readings

• Two weeks of carefully taken glucometer readings (80-100 readings), half pre- and half post-prandial, can be an indicator of your long-term blood glucose level.

• The HbA1c test, taken by your doctor, provides an independent confirmation of how you are doing.

30834512

27731011

24627510

2142409

1832058

1521707

1211356

901005

Whole Blood Glucose level (mg/dL)

Plasma Glucose level (mg/dL)

A1C result (%)

12.2%, my level at diagnosis

9-10%, diabetic average

7%, ADA recommended maximum

5.4%, my average



How Accurate is the A1C test?

• My experience: two tests at two different labs taken 10 days apart: 6.2%, 5.3%

• There are more than 30 different methods to measure A1C.

• Different brands of instruments using the same method can give different results.

• All hemoglobin are not created the same.

• Go to the same lab so that you can compare your results and track changes over time.

• Finger-stick HbA1c meters are as accurate as laboratory meters that use blood from veins.



The DCCT tells us to aim for normal blood glucose

• DCCT: Diabetes Control and Complication Trial

– a ten-year study of 1441 Type 1 diabetics

– to evaluate the effects of improved control of blood glucose

– diabetics split between intensive and conventional therapy

– Intensive group averaged 7% HbA1c; conventional averaged 9% HbA1c

• The reduction in complications was huge in patients with near normal control

– test was stopped early so the results could be made available to all

– reduction in HbA1c corresponded to proportional reduction in risk of complications

– risk of complications drops to zero for normal glucose levels

– Intensive group had 3x higher risk of severe hypoglycemia (BG< 50 mg/dL)

• Any reduction in HbA1c means reduced risk of complications.

– 10% reduction: 30-40% reduced risk of retinopathy (eyes), nephropathy (kidneys), neuropathy (nerves)

– Dropping from a 9% to a 6% HbA1c means a 75% drop in risk of complications.

Bernstein, pp. 37-38



HbA1c test—normal should be your goal

• The average diabetic’s HbA1c test result is 9%.

– Equivalent to greater than 200 mg/dL all the time.

– Twice as much blood glucose as a normal person.

• The ADA’s recommends 7%, but you should do better.

– 7% is not normal.

– Complications will develop slowly.

• A Normal HbA1c—4.8% to 5.8%—should be your goal.

• With today’s glucometers, dieting, exercise and medication, normal is achievable.



Do short term, high blood glucose readings affect your health?

• Because fast-acting insulin does not reduce blood glucose as fast as a normal pancreas, post-prandial spikes in blood glucose can occur.

• Bernstein says that damage done by high blood glucose can be stopped or reversed by returning blood glucose to normal levels.

• How quickly you catch and reduce a high blood glucose level is what matters.

– Frequent testing enables you to spot high glucose levels soon after they occur.

– You reduce your blood glucose level quickly with insulin and/or exercise.

• Short-term spikes in glucose may not influence HbA1c results.

– Glucose takes time to join with blood cell hemoglobin

– Unless blood cells are joined with glucose, they won’t affect your HbA1c.

– However, glucose not joined to hemoglobin is still carried in your blood, and may cause damage to your body.

• My experience—despite my “normal” HbA1c tests and near normal blood glucose control, I developed low level retinopathy in my left eye 7 years after diagnosis.



Short term spikes in blood glucose level can occur when you are most insulin resistant

• Spikes in blood glucose level occur when we are most insulin resistant, which is in the morning for many people.

• 30 minutes after eating breakfast, my glucose level had climbed to 129.

• 1 hour after eating, my level was at 140.

• But 2 hours after eating, it was down to 97.

• A 50% reduction in my breakfast carb intake (to 10 grams) and 10 minutes of exercise after eating reduced the spike from 40 points to just 10 points.



What should you know about glucose testing to manage your diabetes?

• A diabetic who knows his blood glucose level can decide whether he needs to do nothing, take medication, exercise or eat food.

• Successful diabetes management aims for a normal blood glucose level all day, every day.

• Your bedtime test is the most important—your life may depend on it.

• Your blood test results should be kept as part of a written record containing your food intake, medication dosage and level of physical activity.

• The HbA1c test is a diabetic’s report card—it is a measure of “average”blood glucose control over the last 2 to 3 months.

• Any reduction in HbA1c means a reduced risk of complications.

• A Normal HbA1c—4.8% to 5.8%—should be your goal.



Metric Units

• 28 grams (g) = 1 ounce

• 454 grams (g) = 1 pound

• 1 gram (g) = 1000 milligrams (mg)

• 1 liter (L) = 34 ounces

• 1 liter (L) = 10 deciliters (dL)

• Normal blood glucose level: 90 mg/dL



References

1. R. Bernstein, Dr. Bernstein’s Diabetes Solution, Little, Brown and Company, 1997.

2. V. Peragallo-Dittko, “How Accurate is Your Meter,” Diabetes Self-Management, 9/10 2000.

3. M. Nakamoto, “H-B-A-1-C (what it is and why it matters),” Diabetes Self-Management, Jan/Feb 2004, pp. 84-89.

4. S. S. Roberts,”Are A1C Results Reliable,” Diabetes Forecast, March 2005, pp. 23-26.

5. “The Absence of a Glycemic Threshold for the Development of Long-Term Complications: The Perspective of the Diabetes Control and Complications Trial,” Diabetes, Vol. 45, October 1996, pp. 1289-1298.

6. Images from Google™ Image Search at http://images.google.com

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