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How to Diagnose Diabetes

Diabetes is a disease that occurs when the level of glucose in the blood is too high as a result of problems with its metabolism. Different health techniques based on measuring blood glucose levels are carried out to diagnose diabetes. Diabetes is the 7th leading cause of mortality, according to recent studies. This disease can be triggered by different causes and depending on each one, its prevention and diagnosis will differ. Therefore, in order to properly diagnose diabetes, we must know what type it is and its origin.

Another key player we must know in diabetes, besides glucose, is insulin. Insulin is a hormone that helps the glucose to be absorbed by the body’s cells to use it as a source of energy. It is produced in the pancreas, an organ located in the abdominal cavity. In some cases, the body is not able to produce enough or any insulin and therefore, the glucose stays in the blood and does not get internalized by the body’s cells. Other times, the body doesn’t make proper use of insulin causing the same scenario. If this situation is prolonged, the excess glucose in blood can lead to diabetes.

“Symptoms of marked hyperglycemia include polyuria, polydipsia, weight loss, sometimes with polyphagia, and blurred vision. Impairment of growth and susceptibility to certain infections may also accompany chronic hyperglycemia. Acute, life-threatening consequences of uncontrolled diabetes are hyperglycemia with ketoacidosis or the nonketotic hyperosmolar syndrome.

Long-term complications of diabetes include retinopathy with potential loss of vision; nephropathy leading to renal failure; peripheral neuropathy with risk of foot ulcers, amputations, and Charcot joints; and autonomic neuropathy causing gastrointestinal, genitourinary, and cardiovascular symptoms and sexual dysfunction. Patients with diabetes have an increased incidence of atherosclerotic cardiovascular, peripheral arterial, and cerebrovascular disease. Hypertension and abnormalities of lipoprotein metabolism are often found in people with diabetes.

The vast majority of cases of diabetes fall into two broad etiopathogenetic categories (discussed in greater detail below). In one category, type 1 diabetes, the cause is an absolute deficiency of insulin secretion. Individuals at increased risk of developing this type of diabetes can often be identified by serological evidence of an autoimmune pathologic process occurring in the pancreatic islets and by genetic markers. In the other, much more prevalent category, type 2 diabetes, the cause is a combination of resistance to insulin action and an inadequate compensatory insulin secretory response. In the latter category, a degree of hyperglycemia sufficient to cause pathologic and functional changes in various target tissues, but without clinical symptoms, may be present for a long period of time before diabetes is detected. During this asymptomatic period, it is possible to demonstrate an abnormality in carbohydrate metabolism by measurement of plasma glucose in the fasting state or after a challenge with an oral glucose load.”1

 “The chronic hyperglycemia of diabetes is associated with relatively specific longterm microvascular complications affecting the eyes, kidneys and nerves, as well as an increased risk for cardiovascular disease (CVD). The diagnostic criteria for diabetes are based on thresholds of glycemia that are associated with microvascular disease, especially retinopathy. “Prediabetes” is a practical and convenient term referring to impaired fasting glucose (IFG), impaired glucose tolerance (IGT) (1) or a glycated hemoglobin (A1C) of 6.0% to 6.4%, each of which places individuals at high risk of developing diabetes and its complications.”2

Type 1 diabetes mellitus.

“Type 1 diabetes mellitus (juvenile diabetes) is characterized by beta cell destruction caused by an autoimmune process, usually leading to absolute insulin deficiency. Type 1 is usually characterized by the presence of anti–glutamic acid decarboxylase, islet cell or insulin antibodies which identify the autoimmune processes that lead to beta cell destruction. Eventually, all type1 diabetic patients will require insulin therapy to maintain normglycemia.

Type 2 diabetes mellitus.

The relative importance of defects in insulin secretion or in the peripheral action of the hormone in the occurrence of DM2 has been and will continue to be cause for discussion. DM2 comprises 80% to 90% of all cases of DM. Most individuals with Type 2 diabetes exhibit intra-abdominal (visceral) obesity, which is closely related to the presence of insulin resistance. In addition, hypertension and dyslipidemia (high triglyceride and low HDL-cholesterol levels; postprandial hyperlipidemia) often are present in these individuals. This is the most common form of diabetes mellitus and is highly associated with a family history of diabetes, older age, obesity and lack of exercise.”3

“The identification of patients with diabetes or prediabetes by screening allows for earlier intervention, with potential reductions in future complication rates, although randomized trials are lacking to definitively show benefit. The patient described in the vignette has risk factors (obesity, hypertension, and a family history of diabetes) and should be screened. Whether fasting plasma glucose or glycated hemoglobin is measured remains debatable; each test has advantages and disadvantages. Given that the yield of testing is higher when both tests are performed, I typically assess both simultaneously — although most guidelines suggest the use of a single test initially. If the patient has positive results on both tests, the diagnosis is confirmed. If only one test is positive, I would repeat it on a separate day. If diabetes is confirmed, treatment should be initiated on the basis of current guidelines

If prediabetes is identified, a repeat test is not necessary. Lifestyle changes (diet and exercise) should be encouraged; a greater intensity of intervention may be warranted in patients with higher glucose or glycated hemoglobin levels and with additional risk factors, since such findings predict more rapid progression to diabetes. I might consider metformin if progressive increases in glycemic measures were observed during followup, although the FDA has not approved metformin for this indication. Attention should also be paid to other cardiovascular risk factors. I might change the patient’s antihypertensive therapy to an angiotensin-converting–enzyme inhibitor, given the associations between the use of a beta-blocker or thiazide and an increased risk of diabetes in some studies.50 Periodic visits (every 6 to 12 months) are warranted to assess and encourage adherence to lifestyle recommendations and to follow glycemic status.”4

Most health professionals often measure levels of plasma glucose on an empty stomach or the A1C test to diagnose diabetes. It is possible that in some cases, professionals may order a random plasma glucose test. This test consists of measuring the concentrations of glucose in the blood at certain times. It is usually done in the morning after fasting for at least 8 hours, this fasting improvises the reliability of the test.

A1C Test

“The A1C test should be performed using a method that is certified by the NGSP and standardized or traceable to the Diabetes Control and Complications Trial (DCCT) reference assay. Although point-of-care (POC) A1C assays may be NGSP certified, proficiency testing is not mandated for performing the test, so use of POC assays for diagnostic purposes may be problematic and is not recommended. The A1C has several advantages to the FPG and OGTT, including greater convenience (fasting not required), greater preanalytical stability, and less day-to-day perturbations during stress and illness. These advantages must be balanced by greater cost, the limited availability of A1C testing in certain regions of the developing world, and the incomplete correlation between A1C and average glucose in certain individuals. It is important to take age, race/ ethnicity, and anemia/hemoglobinopathies into consideration when using the A1C to diagnose diabetes.”5

The A1C test, also known as the glycosylated hemoglobin test, involves performing a blood test that indicates the blood glucose levels of the past 3 months. When this technique is used to diagnose diabetes, the doctor must take into account patient factors such as age, presence of anemia or other blood problems.

Pregnant women can be tested for oral glucose tolerance test, overload, or both. These tests help professionals know how the body uses glucose.

  • Oral glucose tolerance test: this technique measures blood glucose after fasting for at least 8 hours. First, the blood is measured on an empty stomach and then a liquid with glucose is drank. Then, blood tests are performed every hour. “The Oral Glucose Tolerance Test (OGTT) measures the body’s ability to use a type of sugar called glucose that is the body’s main source of energy. OGTT, a test of immense value and sentiment, in favor of using fasting plasma glucose concentration alone was seen as a practical attempt to simplify and facilitate the diagnosis of diabetes. Hyperglycemia is an important factor in the development and progression of the complications of diabetes mellitus. Diabetes mellitus, one of the most common endocrine metabolic disorders has caused significant morbidity and mortality due to microvascular (retinopathy, neuropathy and nephropathy) and macrovascular (heart attack, stroke and peripheral vascular diseases) complications. The disease is rapidly increasing worldwide and affecting all parts of the world. Due to deficiency of the insulin people suffering from diabetes have high blood glucose level.”6
  • Oral glucose overload test: a blood sample is taken 5 times in a span of 3 hours after having taken a sweet liquid containing glucose. If the glucose level is 135 to 140, it is possible that the test has to be repeated on an empty stomach.

Some main symptoms that are present when suffering from diabetes are: frequent urination, excessive thirst, fatigue, weight loss, increased hunger, blurry vision and slow healing of wounds or infections. If you notice any of these signs, it is better to consult your doctor or specialist so he can perform the test mentioned above.



(1) American Diabetes Association. (2010). Diagnosis and classification of diabetes mellitus. Diabetes care, 33(Supplement 1), S62-S69. Available online at

(2) Punthakee, Z., Goldenberg, R., & Katz, P. (2018). Definition, classification and diagnosis of diabetes, prediabetes and metabolic syndrome. Canadian journal of diabetes, 42, S10-S15. Available online at

(3) Baynes, H. W. (2015). Classification, pathophysiology, diagnosis and management of diabetes mellitus. J diabetes metab, 6(5), 1-9. Available online at

(4) Inzucchi, S. E. (2012). Diagnosis of diabetes. New England Journal of Medicine, 367(6), 542-550. Available online at

(5) American Diabetes Association. (2017). 2. Classification and diagnosis of diabetes. Diabetes care, 40(Supplement 1), S11-S24. Available online at

(6) Sornalakshmi, V., Tresina Soris, P., Paulpriya, K., Packia Lincy, M., & Mohan, V. R. (2016). Oral glucose tolerance test (OGTT) in normal control and glucose induced hyperglycemic rats with Hedyotis leschenaultiana DC. Group, 1, 0-9. Available online at


Robert Velasquez
13 October, 2018

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Hello everyone, my name is Robert Velazquez. I am a content marketer currently focused on the medical supply industry. I studied Medicine for 5 years. I have interacted with many patients and learned a more:

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