This page contains general information about Diabetes mellitus. For more information on specific types, please visit the pages on Diabetes mellitus type 1, Diabetes mellitus type 2, and Gestational diabetes.
Diabetes mellitus Main page
Synonyms and Keywords: Diabetes; DM
Diabetes mellitus (DM) refers to a spectrum of disorders with different metabolic changes that result in hyperglycemia as a common feature. It is caused by interaction of environmental agents in a genetically susceptible person. The metabolic disarrangement that may result in hyperglycemia will define the pathologic feature of each type of DM. Decreased insulin secretion, insulin resistance, decreased glucose utilization and increased glucose production are the main metabolic dysregulations that are known to cause hyperglycemia. Hyperglycemia may cause secondary changes in metabolic arrangement in different systems and it can involve every organ systems. DM is the leading cause of end-stage renal disease (ESRD), nontraumatic lower extremity amputations, and adult blindness worldwide. Accordingly, early diagnosis and treatment can result in significant decrease in mortality and morbidity. The incidence of diabetes has been increasing constantly. According to WHO reports, 346 million people worldwide have diabetes and it is projected to double by 2030. It's prevalence is more in developed countries but the death occurring from DM complications is more common in developing countries. The prevalence of diabetes type 2 is more common than type 1 diabetes. Diabetes can cause many complications. Acute complications (hypoglycemia, ketoacidosis or nonketotic hyperosmolar coma) may occur if the disease is not adequately controlled. Serious long-term complications include macrovascular (coronary heart disease, peripheral arterial disease and cerebrovascular disease), microvascular (retinopathy, neuropathy and nephropathy) and other organ involvement (gastrointestinal, genitourinary, dermatologic, infectious, cataracts, glaucoma, periodontal disease and hearing loss). The main goals of treatment are:
- Elimination of hyperglycemic symptoms
- Control of the long term complications
- Improvement of the patient's quality of life
Diabetes mellitus is classified into 3 types based on the pathogenic process that lead to hyperglycemia.
|Disease||History and symptoms||Laboratory findings||Additional findings|
|Polyuria||Polydipsia||Polyphagia||Weight loss||Weight gain||Serum glucose||Urinary Glucose||Urine PH||Serum Sodium||Urinary Glucose||24 hrs cortisol level||C-peptide level||Serum glucagon|
|Type 1 Diabetes mellitus||+||+||+||+||-||↑||↑||Normal||Normal||N/↑||Normal||↓||Normal||Auto antibodies present
(Anti GAD-65 and anti insulin anti bodies)
|Type 2 Diabetes mellitus||+||+||+||+||-||↑||↑||Normal||Normal||↑||Normal||Normal||↑||Acanthosis nigricans|
|Transient hyperglycemia||-||-||-||-||-||↑||↑||Normal||Normal||↑||Normal||Normal||N/↑||In hospitalized patients especially in ICU and CCU|
|Steroid therapy||+||-||-||-||+||↑||↑||Normal||Normal||↑||↑||N/↑||N/↑||Acanthosis nigricans,|
|RTA 1||-||-||-||+||-||Normal||Normal||↑||Normal||↑||Normal||Normal||Normal||Hypokalemia, nephrolithiasis|
|Glucagonoma||-||-||-||-||-||↑||Normal||Normal||Normal||-||Normal||Normal||↑||Necrolytic migratory erythema|
|Cushing syndrome||-||-||-||-||+||↑||-||Normal||↓||N/↑||↑||Normal||Normal||Moon face, obesity, buffalo hump, easy bruisibility|
Complications of diabetes mellitus may be classified as acute or chronic. Acute complications of diabetes mellitus may occur in type 1, type 2, or gestational diabetes. Chronic complications of diabetes mellitus are more likely to occur in long standing type 1 or type 2 diabetes and may be further classified as macrovascular, microvascular, or other (unspecified etiology) as follows:
They include diabetic ketoacidosis (DKA) and Hyperosmolar hyperglycemic state (HHS). DKA could be the presenting feature of type 1 diabetes and it is more common in type 1 diabetes although, it is sometimes seen in type 2 diabetic patients. HHS is mostly seen in the elderly and it is more common in type 2 diabetes.
- Gastrointestinal (gastroparesis, diarrhea)
- Genitourinary (uropathy/sexual dysfunction)
- Periodontal disease
- Hearing loss
Complications of gestational diabetes differs from type 1 and type 2 diabetes primarily due to its pregnancy-specific effects on the mother as well as its effects on the fetus.
For more information on maternal complications of gestational diabetes click here.
For more information on fetal complications of gestational diabetes click here.
Diabetes mellitus type 1
According to the American Diabetic Association, screening for type 1 DM is not recommended.
Diabetes mellitus type 2
Diabetes screening is recommended for many people at various stages of life, and for those with any of several risk factors. American Diabetes Association Recommendations for Diabetes Screening include:
CATEGORIES OF INCREASED RISK FOR DIABETES (PREDIABETES)
- Screening for prediabetes and risk for future diabetes with an informal assessment of risk factors or validated tools should be considered in asymptomatic adults. B
- Testing for prediabetes and risk for future diabetes in asymptomatic people should be considered in adults of any age who are overweight or obese (BMI $25 kg/m2 or $23 kg/m2 in Asian Americans) and who have one or more additional risk factors for diabetes. B
- For all people, testing should begin at age 45 years. B
- If tests are normal, repeat testing carried out at a minimum of 3-year intervals is reasonable. C
- To test for prediabetes, fasting plasma glucose, 2-h plasma glucose during 75-g oral glucose tolerance test, and A1C are equally appropriate. B
- In patients with prediabetes, identify and, if appropriate, treat other cardiovascular disease risk factors. B
- Testing for prediabetes should be considered in children and adolescents who are overweight or obese (BMI .85th percentile for age and sex, weight for height .85th percentile, or weight.120% of ideal for height) and who have additional risk factors for diabetes (Table 2.5). E
|Criteria for testing for diabetes or prediabetes in asymptomatic adults|
|1. Testing should be considered in overweight or obese (BMI 25 kg/m2 or 23 kg/m2 in Asian Americans) adults who have one or more of the following risk factors:
|2. Patients with prediabetes (A1C 5.7% [39 mmol/mol], IGT, or IFG) should be tested yearly.|
|3. Women who were diagnosed with GDM should have lifelong testing at least every 3 years.|
|4. For all other patients, testing should begin at age 45 years.|
|5. If results are normal, testing should be repeated at a minimum of 3-year intervals, with
consideration of more frequent testing depending on initial results and risk status.
|Categories of increased risk for diabetes (prediabetes)|
|FPG 100 mg/dL (5.6 mmol/L) to 125 mg/dL (6.9 mmol/L) (IFG)|
|2-h PG during 75-g OGTT 140 mg/dL (7.8 mmol/L) to 199 mg/dL (11.0 mmol/L) (IGT)|
|A1C 5.7–6.4% (39–47 mmol/mol)|
All pregnant women should be screened for gestational diabetes in 24-28 weeks with 50 gram glucose test. Measurements greater than 130 mg/dL are considered positive and should proceed to 100 gram glucose test for diagnosis. High risk mothers should be screened as early as the first prenatal visit. These risk factors include:
- A family history of diabetes especially in first degree relatives
- Maternal age >25 yrs
- Certain ethnic groups (such as Native American, Hispanic-American, African-American, South or East Asian, Pacific Islander)
- Body mass index greater than 25 kg/m2
- Gestational diabetes or impaired glucose tolerance test in previous pregnancies
- Previous delivery of a baby >9 pounds
- Personal history of impaired glucose tolerance or impared fasting glucose (pre-diabetes)
- Glycosuria at the first prenatal visit
- Certain medical conditions (such as metabolic syndrome, polycystic ovary syndrome (PCOS), current use of glucocorticoids, hypertension)
- Previous history of unexplained miscarriage or stillbirth
- Smoking doubles the risk of gestational diabetes
- Multiple gestation
- Genetic predisposition (.e.g. glucokinase mutation)
Diabetes mellitus type 1 and type 2
A fasting plasma glucose (FPG) <5.6 mmol/L (100 mg/dL), a plasma glucose <140 mg/dL (11.1 mmol/L) following an oral glucose challenge and an HbA1c <5.7% are considered normal.
Diagnostic criteria for DM are:
- Symptoms of diabetes plus random blood glucose concentration ≥11.1 mmol/L (200 mg/dL)† OR
- Fasting plasma glucose ≥7.0 mmol/L (126 mg/dL)‡ OR
- Hemoglobin A1c ≥ 6.5% OR
- 2-h plasma glucose ≥11.1 mmol/L (200 mg/dL) during an oral glucose tolerance test¶
American Diabetes Association Diabetes Diagnostic Criteria 2018 (DO NOT EDIT)
|Level of evidence||Description|
|E||Expert consensus or clinical experience|
Recommendations for Hb-A1c:
- To avoid misdiagnosis or missed diagnosis, the A1C test should be performed using a method that is certified by the NGSP and standardized to the Diabetes Control and Complications Trial (DCCT) assay. B
- Marked discordance between measured A1C and plasma glucose levels should raise the possibility of A1C assay interference due to hemoglobin variants (i.e., hemoglobinopathies) and consideration of using an assay without interference or plasma blood glucose criteria to diagnose diabetes. B
- In conditions associated with increased red blood cell turnover, such as sickle cell disease, pregnancy (second and third trimesters), hemodialysis, recent blood loss or transfusion, or erythropoietin therapy, only plasma blood glucose criteria should be used to diagnose diabetes. B
†:Random is defined as without regard to time since the last meal.
‡:Fasting is defined as no caloric intake for at least 8 h.
¶:The test should be performed using a glucose load containing the equivalent of 75 g anhydrous glucose dissolved in water, not recommended for routine clinical use.
American Diabetes Association Diabetes Diagnostic Criteria 2018 (DO NOT EDIT)
|Criteria for the diagnosis of diabetes|
|FPG ≥126 mg/dL (7.0 mmol/L). Fasting is defined as no caloric intake for at least 8 h.|
|2-h Plasma Glucose (PG) ≥200 mg/dL (11.1 mmol/L) during an OGTT. The test should be performed as described
by the WHO, using a glucose load containing the equivalent of 75 g anhydrous glucose dissolved in water.
|A1C ≥6.5% (48 mmol/mol).
|In a patient with classic symptoms of hyperglycemia or hyperglycemic crisis, a random plasma glucose ≥200 mg/dL (11.1 mmol/L).|
There are 2 strategies to confirm the GDM diagnosis.
- One-step 75-g Oral glucose tolerance test (OGTT)
- Two-step approach with a 50-g (nonfasting) screen followed by a 100-g OGTT for those who screen positive.
One Step Strategy
Perform a 75 g glucose tolerance test in 24-28 weeks of pregnancy and read the measures 1 h and 2 h after glucose ingestion as well as fasting glucose. The OGTT should be performed in the morning after an overnight fast of at least 8 h. The diagnosis of GDM is made when any of the following plasma glucose values are met or exceeded:
- Fasting: 92 mg/dL (5.1 mmol/L)
- 1 h: 180 mg/dL (10.0 mmol/L)
- 2 h: 153 mg/dL (8.5 mmol/L)
Two Step Strategy
In this approach, screening with a 1 h 50-g glucose load test (GLT) followed by a 3 h 100-g OGTT for those who screen positive.
The diagnosis of GDM is made when at least 2 out of 4 measures of 3 h 100-g OGTT became abnormal.
- The following table summarizes the diagnostic approach for gestational diabetes.
|Cut off (mg/dl)|
|Fasting||1 Hour||2 Hour||3 Hour|
Life style modification is the mainstay of prevention of diabetes mellitus. It includes, changes in diet, weight reduction and exercise. The strongest evidence for diabetes prevention comes from the Diabetes Prevention Program (DPP). The DPP demonstrated that an intensive lifestyle intervention could reduce the incidence of type 2 diabetes by 58% over 3 years.
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