Hyperglycemia (High blood sugar)

Dr. Srishti GuptaMBBS

May 31, 2021

January 29, 2024


Hyperglycemia is the medical term used to describe an elevated or high blood level of glucose. Elevation of blood glucose can be transient or short-lived, as is the case after eating a meal, or associated with endocrine disorders affecting glucose metabolism of the body. The normal blood glucose level in healthy adults is less than 100mg/dL while on an empty stomach (i.e. upon waking in the morning after 8 hours or more of fasting, before breakfast) and less than 140 mg/dL two hours after eating a meal. Hyperglycemia is a commonly encountered problem in patients suffering from diabetes mellitus (type 1, type 2 and gestational diabetes mellitus) due to insulin deficiency and insulin resistance. Insulin is a hormone secreted by the beta islet cells in the pancreas and its action is metabolism and regulation of glucose uptake by cells of the body. Type 1 diabetes occurs due to an immune cell (autoantibody) mediated destruction of insulin-secreting cells; the resulting insulin deficiency inhibits the uptake of glucose by the body, leading to an increase in glucose circulating in the blood. Whereas in type 2 diabetes, insulin resistance develops generally due to poor lifestyle and obesity, inhibiting the hormone’s action on glucose blood levels. Gestational diabetes mellitus refers to the state of high blood glucose levels that develops in some pregnant women due to increased insulin resistance.

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Although elevated blood glucose levels are pathognomonic of diabetes mellitus, usually with oral hypoglycemic agent (OHA) drugs like metformin and/or insulin, the blood glucose levels are maintained at the lowest possible levels for the patient. However, under some circumstances, like a skipped dose, a heavy meal or any other cause of acute stress on the body, blood glucose levels can rise uncontrollably. Diabetic ketoacidosis (DKA) and Hyperosmolar Hyperglycaemic Syndrome (HHS) are two dreaded complications of uncontrolled surges of blood glucose levels in diabetic patients. While diabetes mellitus is always associated with hyperglycemia, other non-diabetic conditions can also cause an abnormal increase in blood glucose levels.

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Signs and symptoms of hyperglycemia

Although the underlying causes of hyperglycemia differ, the state itself invariably presents the same way in most cases. Common signs and symptoms of hyperglycemia include, but are not limited to, the following:

Clinical features of altered mental status are possible with extremely high blood glucose levels. Some features to look out for are:

  • Drowsiness and lethargy
  • Delirium
  • Coma
  • Focal or generalized seizures 
  • Visual changes or disturbances
  • Hemiparesis, or weakness on one half of the body
  • Sensory deficits in vision or touch sensation

Hyperglycaemia, especially when due to diabetic ketoacidosis and hyperosmolar hyperglycaemic state, is a medical emergency; the patient should immediately be taken to the hospital for treatment if it is suspected.

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Causes and risk factors of hyperglycemia

Hyperglycaemia or raised blood glucose can occur as a result of diabetes mellitus and other health conditions. Following are possible causes of raised blood glucose levels:

  • Diabetic Ketoacidosis (DKA): DKA is a dangerous and potentially life-threatening complication of poorly controlled blood glucose levels in diabetic patients. As diabetic ketoacidosis develops due to an unduly low level of insulin, it is more common in patients with type 1 diabetes mellitus but can also sometimes occur in patients with type 2 diabetes mellitus. DKA is a medical emergency and requires hospital admission and urgent treatment. In such cases, blood glucose levels tend to be more than 250mg/dL, blood pH is acidic (less than 7.3) and mild to moderate levels of ketone bodies are found in urine. The mainstay of treatment is intravenous fluid therapy and insulin administration. Serum potassium level can fall (hypokalemia) due to treatment with fluids and insulin and may have to be corrected to prevent adverse effects. Sodium bicarbonate may be used to correct the acidic blood pH in DKA. Risk factors for developing DKA include:
    • Untreated or undiagnosed type 1 diabetes mellitus
    • Frequently missed insulin doses
    • Not taking insulin as prescribed or not taking insulin at all
    • Stomach illness with a lot of vomiting
    • Significant illness or trauma putting the body under stress
    • Infections such as pneumonia, urinary tract infection or sepsis
    • Heart disease, such as heart attack
    • Pulmonary embolism
    • Recent stroke
    • Pregnancy
    • Surgery
    • Use of some medicines, like corticosteroids, steroids and antipsychotic drugs
    • Recreational drug use, such as cocaine
  • Hyperosmolar Hyperglycemic State (HHS): Another hyperglycemic complication of diabetes mellitus is hyperosmolar hyperglycaemic state (HHS). Unlike diabetic ketoacidosis, HHS is more common in type 2 diabetes mellitus patients and associated with a much higher blood glucose level (more than 600 mg/dL). Extreme hyperglycemia causes extreme dehydration and altered mental status in patients. However, the blood pH is not acidotic nor does the urine contain ketone bodies. Management involves intravenous fluid therapy to correct dehydration and altered mental status. Risk factors that can precipitate HHS are similar to those of diabetic ketoacidosis (DKA) and include: 
    • Frequently missed oral diabetic medicines or insulin
    • Untreated or undiagnosed diabetes mellitus
    • Stroke
    • Intracranial hemorrhage
    • Silent myocardial infarction or heart attack
    • Pulmonary embolism
    • Acute or chronic pancreatitis
    • Infections like pneumonia, sepsis
    • Internal hemorrhage
    • Burns
    • Dialysis (peritoneal and hemodialysis)
    • Some medications like corticosteroids, antipsychotics, beta-blockers, osmotic agents like mannitol and antiarrhythmic drugs
    • Alcohol use
  • Stress-induced hyperglycemia: Elevation of blood glucose levels due to state of acute stress to the body, as with injury or illness, is termed as stress-induced hyperglycemia. Although also monikered stress diabetes, this condition is not the same as diabetes mellitus. Usually, elevated blood glucose levels of stress-induced hyperglycemia are incidental findings when blood tests are run in the hospital setting after an illness or injury that resolves once the period of stress ends. Patients who develop hyperglycemia when under acute stress are also likely to develop diabetes mellitus later in life. Risk factors that can lead to one developing stress-induced hyperglycaemia when injured or ill include undiagnosed prediabetes or impaired glucose metabolism. A recent study has discovered that hyperglycemia that is induced after a patient experiences an acute stroke can worsen the outcome if not corrected as soon as possible.
  • Corticosteroid induced hyperglycemia: Corticosteroids, or steroids, are useful and potent drugs that stop harmful inflammation. They are often prescribed, for short periods of time, for allergic or autoimmune diseases. However, corticosteroids have a well documented adverse effect on glucose metabolism and produce hyperglycemia. Although steroid-induced hyperglycemia usually resolves once the therapy is stopped, with extended periods of use of three months or more, a fraction of patients can go on to develop full-blown diabetes mellitus.
  • Hyperglycemia in preterm newborn baby: Raised blood glucose levels in newborn babies, or neonatal hyperglycemia, is common in Very Low Birth Weight (VLBW) babies (weighing less than 1500 grams) or extremely preterm babies (born before 28 weeks of gestation). Newborn babies’ bodies maintain the glucose levels by balancing the rate of glucose breakdown and glucose synthesis; however, in extremely premature babies, this mechanism is not fully developed and hypoglycemia (low blood glucose levels) or hyperglycaemia (high blood glucose levels) can occur. Although hypoglycemia is more common, hyperglycemia can also occur. However, hyperglycemia can occur in newborn babies secondary to acute stress, such as respiratory distress syndrome or sepsis. Normal blood glucose level for a newborn is considered to be between 70 mg/dL to 150 mg/dL. A newborn baby with hyperglycemia may have no signs and symptoms at all. Sometimes, babies with high blood sugar will produce large amounts of urine and become dehydrated.
  • Pancreatitis: Pancreatitis refers to the condition of inflammation of the pancreas. It may be acute or chronic with acute attacks. The most common causes of pancreatitis are gallstones or heavy alcohol use. The digestive enzymes that the pancreas produce normally can damage the insulin-producing cells present in the pancreas, in the case of pancreatitis. Pancreatic diabetes can thus set in. Unlike the more traditional, diabetes mellitus type 2, the management of pancreatic diabetes is through diet modification, pancreatic enzyme supplementation and sometimes insulin as well. Risk factors that can cause hyperglycemia to occur after a single episode of acute pancreatitis include: 

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Diagnosis of hyperglycemia

Diagnosis of hyperglycemia is either made upon the basis of suspected symptoms or incidentally when conducting blood tests. When a patient reports to the hospital with signs and symptoms of hyperglycemia, the doctor begins by taking a thorough medical history, paying special attention to any preexisting lifestyle diseases (like diabetes mellitus) and recent history of illness, injury, surgery or pregnancy. History is also taken of the medications the patient takes as well as his or her compliance with the prescribed drugs. A clinical physical examination follows the history with the aim to elicit signs of dehydration and possible underlying causes. The patient’s mental status is made a note of and neurological tests are also conducted. Definitive diagnosis is made through blood and urine investigations.

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Tests for hyperglycemia

After assessing the patient clinically, laboratory investigations are ordered. The following investigations are conducted routinely in a patient with suspected hyperglycemia to reach a diagnosis and guide treatment.

  • Blood tests
    • Random blood glucose levels: The normal random blood glucose level should be below 200 mg/dL in healthy adults. Blood glucose levels above 250 mg/dL are usually found in diabetic ketoacidosis and above 600 mg/dL in a hyperosmolar hyperglycaemic state. Normal blood glucose levels in newborn babies are between 70 mg/dL and 150mg/dL. Blood glucose levels above the normal imply hyperglycemia.
    • Fasting blood glucose: When blood glucose levels are tested on an empty stomach (after at least 8 hours since the last meal) the normal blood glucose levels are between 70mg/dL to 100 mg/dL in healthy adults.
    • Postprandial blood glucose: Blood glucose levels two hours after eating a meal are less than 140 mg/dL in healthy adults.
    • Oral glucose tolerance test: This is the definitive test to diagnose diabetes mellitus. A patient on an empty stomach (at least 8 hours since the last meal) is made to consume 75 grams of glucose solution and blood glucose levels are tested.
    • HbA1c: Hemoglobin, the red oxygen-carrying pigment of blood, becomes glycosylated when glucose levels in the blood are high. Glycosylated hemoglobin gives an idea of the long-term blood glucose control and levels below 6.5% are normal. 
    • Full blood count: Raised white blood cell counts can imply the presence of infection in the body.
    • Arterial blood gas: This investigation gives information about the blood pH and electrolyte concentration. Metabolic acidosis in diabetic ketoacidosis (DKA) can be diagnosed.
    • Serum electrolytes: Dehydration can cause derangement of blood electrolytes. Potassium levels can dip due to intravenous fluid therapy and insulin used in treating hyperglycaemia.
  • Urine tests
    • Urine glucose: When blood glucose levels are more than 180 mg/dL, glucose begins to appear in the urine.
    • Urine ketone bodies: Ketone bodies are formed due to glucose metabolism impairment. Appearance in urine implies a very high blood level.
    • Urine routine microscopy: Pus cells or red blood cells may be present in case of urinary tract infections.
    • Urine culture and sensitivity: Urinary tract infections can be diagnosed through this and treated with the appropriate antibiotic.
  • Radiological imaging tests
    • Chest X-ray: Underlying chest infections like pneumonia can be diagnosed if present.
    • CT scan abdomen: It can help detect any underlying infectious pathology as well as acute or chronic pancreatitis.
    • Ultrasound abdomen: It serves the same purpose as CT scans but is considered safe to use in pregnancy.
    • ECG: Sometimes, a hyperosmolar hyperglycaemic state can develop following a silent myocardial infarction (heart attack) and an electrocardiogram can help rule it out.

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Management of hyperglycemia

Even though the mainstay of treatment is specific to the underlying disease or problem, correction of high blood glucose levels in medical emergencies (like diabetic ketoacidosis and hyperosmolar hyperglycaemic state) remains the same.

  • Fluid therapy: In order to correct the blood osmolality and dehydration intravenous fluid therapy is the very first step. Usually, fluid therapy is started with the use of normal saline for a few hours, after which the blood glucose levels are checked. Once the blood glucose levels have reduced to an appropriate level, normal saline is substituted with intravenous dextrose solution to prevent fluid overload and cerebral edema that can occur with excessive saline.
  • Insulin: To adequately control the blood glucose levels after addressing dehydration, insulin therapy is the second step. Intravenous insulin is administered first, bolus followed by infusion. Once the patient has stabilised and has resumed eating meals, subcutaneous insulin injections are started. The aim is to maintain a window of overlap between intravenous and subcutaneous insulin to ensure adequate glycaemic control.
  • Electrolyte correction: Due to insulin therapy the serum potassium levels can fall, sometimes even dangerously so. Depending on the potassium level, potassium supplementation with KCl is started. Sodium bicarbonate can also become reduced due to acidosis and may need replacing.
  • Antibiotics: If the precipitating cause of hyperglycaemia was an infection, appropriate antibiotics must be started.
  • Anticoagulants: The risk of thrombosis and myocardial infarction increases after extreme hyperglycemia and sometimes an anticoagulant may be prescribed for prevention.

(Read more: Self-monitoring of blood glucose)

Prevention of hyperglycemia

While not much can be done to prevent hyperglycemia that is induced by illness, injury or essential medications, medical emergencies due to hyperglycemia in diabetes mellitus patients can be prevented by:

  • Ensuring timely dose of insulin or oral hypoglycemic agent (OHA)
  • Regularly checking blood glucose levels at home with a glucometer
  • Exercising and reducing weight
  • Eating a healthy diet
  • Not consuming too many calories in a meal
  • Eating the right carbohydrates
  • Not taking too much stress
  • Ensuring regular health checkups and appointments with the doctor

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Complications associated with hyperglycemia

A few complications of hyperglycemic medical emergencies include: 

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Medicines for Hyperglycemia (High blood sugar)

Medicines listed below are available for Hyperglycemia (High blood sugar). Please note that you should not take any medicines without doctor consultation. Taking any medicine without doctor's consultation can cause serious problems.

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