Overview

Over 2 million Canadians have diabetes. There are three main forms of this condition.

Type I:  This occurs when the body fails to produce insulin.  As insulin is required to control (lower) the blood glucose by making it available for metabolism, a lack of insulin allows the glucose to rise to uncontrolled levels.  Ironically, though the blood has too much glucose, the tissues do not have enough and they begin to metabolize fat in order to get energy.  This results in the production of ketones that may cause metabolic crises and even death.  Insulin injections are required for treatment.

Type II:  Most people with diabetes have this form.  This is the variety developed later in life that was formerly called “adult onset” diabetes.  In Type II the body can still produce insulin but it either does not produce enough or the insulin it does produce is not used effectively. The result is ineffective utilization of glucose that rises to elevated levels in the blood stream.  It can often be treated by diet and weight loss to reduce the demand for insulin, but treatment with insulin may be required.

The third type of diabetes is a temporary situation that occurs in pregnancy known as gestational diabetes.  It is found in 2-4% of all pregnancies and poses a risk to the well being of the fetus.  It is standard practice to screen for the presence of this condition in all pregnancies during the first or second trimesters.

The symptoms of diabetes vary.  Some persons with Type II or gestational diabetes have no symptoms at all but are still at risk from the long-term complications of the disorder. When the symptoms become overt, the patient feels unwell, is very thirsty, excretes abnormally large volumes of urine, experiences unexplained weight loss, and may suffer serious metabolic disturbances.

Diagnosis

The diagnosis of diabetes is confirmed with laboratory tests.  Screening for diabetes is recommended (at a minimum) every three years in individuals ≥ 40 years of age.

A patient with metabolic decompensation and unequivocal hyperglycemia may be diagnosed as diabetic with a single glucose measurement.  All other patients must have two venous plasma glucose measurements.  The diagnosis of diabetes can be made if one of the following sets of criteria are met:

1.       Symptoms of diabetes plus a random plasma glucose ≥11.1 mmol/L

2.       Fasting plasma glucose ≥7.0 mmol/L

3.       Plasma glucose ≥11.1 mmol/L in the 2-hour sample of the 75g oral glucose tolerance test

Refer to page S15 of the 2008 Canadian Diabetes Guidelines for more information on the diagnosis of diabetes as well as the related conditions ‘impaired fasting glucose’ and ‘impaired glucose. 

To diagnose gestational diabetes, all pregnant women should undergo a Gestational Diabetes Screening Test between 24 and 28 weeks’ gestation unless they have multiple risk factors, in which case the Screening Test should be performed during the first trimester.  In the Screening Test, the pregnant woman consumes a 50-gram glucose drink and the blood glucose level is measured after one hour.  The test may be performed at any time of the day and fasting is not required.  If the glucose level exceeds 7.7 mmol/L, then a Glucose Tolerance Test should be carried out: however, a level greater than 10.3 mmol/L is diagnostic of gestational diabetes and further testing is not required.  Unless specified otherwise by the physician, this Tolerance Test requires the patient to be fasting and consists of measurements of blood glucose before and then 1h, 2h and 3h following a 100-gram glucose drink.  If two or more levels exceed their designated targets, a diagnosis of Gestational Diabetes is made.  A physician may elect to treat a patient as a diabetic if the values get close to these limits.

Refer to page S168 of the 2008 Canadian Diabetes Guidelines for more information on the diagnosis of gestational diabetes.  Note that since the Glucose Tolerance Test is a 100-gram / 3h procedure as per consensus of BC laboratory physicians (rather than 75-gram / 2h, as suggested by the Canadian Diabetes Association), different target values apply: these may be found here.

Monitoring Diabetes

Once diabetes is diagnosed, therapy may be instituted. Most monitoring of insulin therapy is carried out by the patient with a glucose meter. There are two additional tests that are recommended for all Type I and Type II diabetics on a regular basis: glycated hemoglobin (in blood) and microalbumin (in urine).  Monitoring information specific to British Columbia may be found at the BC Ministry of Health Services site. 

Glycated Hemoglobin

The Glycated Hemoglobin test (also known as Hemoglobin A1c or Hb A1c) should be carried out every three months.  In this test, blood is drawn and analyzed for the amount of glucose that has become attached to the hemoglobin molecule.  Normally, not more than 6% of hemoglobin molecules have glucose attached; diabetics will have higher percentages.  The percentage is related to the “average” blood glucose level and is therefore an indication of overall glucose control. It should be noted that the percentage is reported not as a percentage but as a decimal (e.g. 6% will be reported as 0.06).  If the Glycated Hemoglobin result is too high, more stringent insulin therapy is required. The Glycated Hemoglobin test should not be used for the diagnosis of diabetes as there are no recognized standards for using it in this context.  

Microalbumin

The other monitoring test for diabetes complications is urinary microalbumin.  Despite its name, ‘microalbumin’ is identical to the protein albumin present in blood: the ‘micro’ prefix refers to the fact that its levels in urine are about 1000-fold lower than those in blood.  The lab measures the amount of albumin in the urine sample and reports the result as a ratio to creatinine (a substance excreted at a constant amount) to correct for the variable dilution of urine. If the albumin-creatinine ratio exceeds 2.8 (females) or 2.0 (males), further testing may be carried out.  The presence of abnormally high levels of urinary microalbumin indicates that diabetes is beginning to affect the kidney and therapy to prevent the rapid development of kidney problems should be initiated.

Useful information about diabetes can also be obtained from the Canadian Diabetes Association  and the American Diabetes Association.