Your source for clinical lab test information.

Sample

Stability of sample

Indication

Pathophysiology

  1. The carbohydrates are major components of the diet and are an important source of energy.
  2. The capacity of the body to store the carbohydrate is limited:
    1. The liver can store only 10 % of its wet weight.
    2. Muscle can store 5% of its wet weight.
    3. This store amount is only sufficient for half a day.
  3. Carbohydrates include sugar and starch.
    1. The function of the carbohydrates is:
      1. Components of RNA and DNA.
      2. Source of energy from the glucose.
        1. Under fasting conditions the following organs depend only upon the glucose as a source of energy:
          1. The brain is the main organ dependant on the glucose.
          2. Red blood cells.
          3. White blood cells.
          4. Platelets.
          5. Kidney medulla.
    2. Glucose is formed by the breakdown of :
      1. Grains.
      2. Starchy vegetables.
      3. Legumes.
      4. Body store of glycogen.
      5. Endogenous proteins.
    3. Increased glucose level leads to its storage as glycogen in the liver.
      1. Decreased glucose level leads to glycogenolysis and forms glucose from the glycogen.

      1. Excess of glucose is converted into fat by adipose cells and stored in the adipose tissue.   
      2. Triose pathway is the main junction where four pathways intersect and help to maintain the glucose level.
        1. This is the complicated enzymatic system but the glucose level is maintained in the normal range.

                       

  1. The glucose metabolism is interlinked with fats and proteins, as shown in the following two diagrams.

  

  1. Glucose levels are controlled by insulin and glucagon.
  2. Glucagon
    1. Glucagon is produced by the Alpha cells of islets of Langerhans in the pancreas.
    2. It breaks glycogen to glucose in the liver.
      1. It will lower the plasma glucose level.
      2. In the case of fasting, protein and fats are broken down into glucose under the influence of Glucagon.
  1. Insulin
    1. Insulin is produced by the beta cells of islets of Langerhans in the pancreas.
    2. It attaches to the insulin receptors on muscles, liver, and fatty cells.
    3. It pushes the glucose into the cells to be metabolized to glycogen, amino acid, and fatty acids.
    4. Insulin lowers the plasma glucose level.

    1. Increased insulin will lower the blood glucose level and deficiency will increase glucose.

 

  1. Other hormones like Adreno-corticosteroids, ACTH, epinephrine, thyroxine, can affect glucose metabolism.
    1. The above hormones increase the plasma glucose level.
  2. Serum glucose level is dependant upon the time and relation to food intake.
  3. Glucose level is low in the fasting state.
    1. Glucose goes to the normal state after 2 hours of the food intake. 

                                           

  1. The concentration of glucose is higher in arterial blood than venous.
  2. When glucose is around 126 mg/dl then try to estimate glucose level after oral 75 grams of glucose.
    1. Now check one hour and two-hour samples.
    2. This oral glucose test will pick up Impaired Glucose Tolerance cases, where you can prevent the development of Diabetes Mellitus.
  3. When the fasting level is between 100 to 126 mg/dl is called fasting hyperglycemia.  

Normal fasting glucose level

Source 1

Age mg/dL
Cord blood 45 to 96
Premature 20 to 60
Neonates 30 to 60
Newborn 1 day 40 to 60
>one day 50 to 80
Child  60 to 100
Adult  74 to 104
60 to 90 years 82 to 115
>90 years 75 to 121

Definition of diabetes mellitus

Latest classification criteria for diabetes mellitus

  1. Diabetes mellitus:
    1. If fasting glucose level 126 mg/dl or above should be labeled as D. Mellitus (when this value is found two times).
    2. One random glucose level of more than 200 mg/dl with symptoms of polyuria, polydipsia, and polyphagia are considered diagnostic of diabetes.
    3. HbA1c more than 6.5 % diagnostic for Diabetes.
    4. The 2-hour postprandial glucose level of more than 200 mg/dl during OGTT.
  2. Impaired fasting glucose = > 126 mg/dl.
  3. Impaired glucose tolerance when:
    1. Fasting glucose < 126 mg/dl
    2. OGTT 2 hours sample is 140 mg to 199 mg/dl.

Criteria for the diagnosis of diabetes mellitus

Diagnosis Fasting glucose level Random glucose level 2 hour glucose level (in OGTT) HbA1c 
Normal  <100 mg/dL  (5.6 mmol/L)   <14o mg/dL (7.8 mmol/L) <5.7
Prediabetics 100 to 125 mg/dL (5.6 to 6.9 mmol/L) ≥140 to 199 mg/dL (7.8 to 11.0 mmoml/L) ≥140 to 199 mg/dL (7.8 to 11.0 mmol/L) 5.7 to 6.4%
Diabetes mellitus ≥ 126 mg/dL (7.0 mmol/L) 200 mg/dL (11.1 mmom/L) ≥200 mg/dL (11,1 mmol/L) ≥6.5%

Types of Diabetes mellitus

  1. Diabetes mellitus type I (Insulin dependant , IDDM) . The possible eitiolgy is :
    1. immune mediated.
    2. Idiopathic.
    3. This is also called Juvenile diabetes and seen under the age of 20 years.
    4. There is the destruction of the beta cells of the pancreas.
    5. These patients are dependent on exogenous insulin on surviving.
  2. Diabetes mellitus type II (Non-insulin dependant , NIDMM).
    1. There is around 90% prevalence.
    2. This is seen in the adults after the age of 20 years. Mostly seen after 40 years of age.
    3. There is a decreased amount of insulin or there is insulin resistance.
    4. DM type II can be controlled by diet, exercise, or oral hypoglycemic agents and in some cases may need insulin. 
  3. Gestational diabetes mellitus (GDM):
    1. There is around 3% pregnancies prevalence.
    2. This is seen during pregnancy and resolve after the delivery.
    3. There is insulin resistance.
    4. These patients may be controlled by diet or oral hypoglycemic agents and in some cases may need insulin.
  4. Impaired fasting glucose (IFG). This is a prediabetic group who have a significant risk of developing diabetes mellitus. On 75 gram OGTT, the fasting level is 100 to 125 mg/dL. 

Factors affecting glucose level

  1. Stress like trauma, general anesthesia, infection, burns, and Myocardial infarction can Increase the glucose level.
  2. Caffeine may increase the level.
  3. Some of the pregnant women may experience glucose intolerance. In the case of the raised significant level is called Gestational diabetes.
  4. Drugs May increase the glucose level like antidepressant (tricyclic), Beta blockers, corticosteroids, I/V glucose, dextrothyroxine, diazoxide, diuretics, estrogen, glucagon, isoniazid, lithium, phenothiazine, phenytoin, and salicylates intoxication.
  5. Drugs may decrease the glucose level like acetaminophen, alcohol, anabolic steroids, insulin, tolbutamide, propranolol, and clofibrate.

Normal

  1. Usually, glucose between 70 to 110 mg/dl is considered normal.
  2. Fasting glucose = < 100 mg/dl.
    1. Cord blood = 45 to 96 mg/dL  (2.5 to 5.3 mmol/L)
    2. premature baby = 20 to 60 mg/dL.  (1.1 to 3.3 mmol/L).
    3. Neonates = 30 to 60 mg/dL  (1.7 to 3.3 mmol/L).
  3. Infants = 40 to 90 mg/dL  (2.2 to 5.0 mmol/L).
  4. Child <2 years = 60 to 100 mg/dL  (3.3 to 5.5 mmol/L).
    1. Child >2 years = like adult level.
  5. Adult fasting = 70 to 110 mg/dL  (<6.1 mmol/L).
    1. Adult random = <160 mg/dL  (11.1 mmol/L).
Diagnosis  Fasting glucose level Random / non fasting glucose level  2 hours glucose after 75 grams of oral test  
Diabetes mellitus >125 mg/dL >199 mg/dL >199 mg/dL
Pre-diabetes (impaired fasting glucose) >99 mg and <125 mg/dL -  
Pre-diabetes (impaired glucose tolerance)     >139 mg and <200 mg/dL

Glucose values in whole blood and serum 

Fasting Child mg/dL Adult mg/dL
Serum or plasma 60 to 105  70 to 100
Whole blood 50 to 90 60 to 100
2 hours, postprandial    
Serum or plasma around 150 around 140
Whole blood around 120 around 120


Diabetes Mellitus classification on the basis of  oral 75 G Glucose overload

Patterns of Glucose Fasting glucose mg/dL Postprandial glucose mg/dL 2 hours glucose mg/dL
Normal <115 <200 <140
Diabetes Mellitus >140 >200 >200
Impaired glucose tolerance <140 >200 140 to 190

Critical values of Glucose :

  Critical low glucose level mg/dL Critical high glucose level mg/ dL
Adult male < 50  > 400
Adult female < 40 > 400
Infants < 40  
Newborn < 30 > 300

Raised glucose level (Hyperglycemia) seen in:

  1. Diabetes mellitus, adult and juvenile.
  2. Physiological causes.
    1. Strenuous exercise.
    2. Strong emotions.
    3. Shock and burns.
    4. Infections.
  3. Endocrine disorders.
    1. Thyrotoxicosis
    2. Acromegaly and gigantism.
    3. Pheochromocytoma.
    4. Cushing’s syndrome.
  4. Pancreatic diseases.
    1. Acute and chronic pancreatitis.
    2. Pancreatitis due to mumps.
    3. Cystic fibrosis.
    4. Hemochromatosis.
    5. Pancreatic cancers.
  5. other causes are:
    1. Cerebrovascular accident.
    2. Chronic liver disease.
    3. Chronic renal disease.
    4. Acanthosis nigricans.

Decreased glucose level (Hypoglycemia) seen in:

  1. Pancreatic disorders.
    1. Islet Cell Tumor.
    2. Glucagon deficiency.
  2. Tumors.
    1. Adrenal gland carcinoma.
    2. carcinoma of stomach.
    3. Fibrosarcoma.
  3. Liver diseases.
    1. In poisoning e.g. arsenic, chloroform, carbon tetrachloride, phosphorus, salicylates, antihistamines, phenformin, and alcohol.
  4. Endocrine disorders.
    1. Hypopituitarism.
    2. Addison’s disease.
    3. hypothyroidism.
  5. Functional disorders.
    1. Postgastrectomy.
    2. Gastroenterostomy.
    3. Autonomic nervous system disorders.
  6. Pediatric causes.
    1. Prematurity.
    2. Infant diabetic mothers.
    3. Idiopathic leucine sensitivity.
  7. Enzyme deficiency.
    1. Galactosemia.
    2. Fructose intolerance.
    3. Von Gierke’s syndrome.

Complication of Diabetes Mellitus: 

  1. There may be hypoglycemia.
  2. In patients with hyperglycemia of Type I left uncontrolled, they may develop life-threatening complications like diabetic Ketoacidosis.
    1. Without treatment, the patient may become acidotic and dehydrated and may lose consciousness.
  3. Type II may develop hyperosmolar coma.
  4. Peripheral neuropathy.
  5. Diabetic retinopathy and cataract formation.
  6. Cardiovascular microangiopathy.
    1. Coronary atherosclerosis.
    2. Myocardial infarction is 3 to 5 times more common in diabetic patients.
    3. AMI is the leading cause of death in patients with diabetes mellitus type 2.
  7. Peripheral vascular diseases like ischemia of lower extremities, erectile dysfunction, and intestinal ischemia.
    1. Gangrene of the foot.
  8. Diabetic kidney diseases.
  9. Chronic pyogenic skin infection.
    1. Candidal infection of the skin.
  10. Bone and joints show contracture.

Monitoring of diabetes mellitus:

  1. In the newly diagnosed patient check glucose frequently.
  2. The best timings are:
    1. Before meals.
    2. At bedtime.

Possible References Used

Back to tests