If you have been told by the doctor that you have high blood sugar, diabetes, pre-diabetes, or borderline blood sugar values, then it is in your best interest to learn how to take care of your health.

Diabetes is a pancreatic and vascular disease that makes it difficult for the body to absorb and break down sugars (monosaccharides and polysaccharides, mostly found in high carbohydrate foods). For a diabetic, these sugars stay in the bloodstream, leading to high blood sugar (hyperglycemia) and subsequent consequences.

Currently, 8.8% of Canadians have diabetes. And 549 people in Canada get newly diagnosed every day.

Diabetes is not the only cause of high blood sugar, known as hyperglycemia, but most people with diabetes have to carefully monitor their blood sugar. When a person has diabetes, their bodies do not produce enough insulin to process sugar normally, leading to hyperglycemia.

It is important for a person with diabetes to monitor hyperglycemia because high blood sugar can lead to eye, kidney, heart, limb, or blood vessel damage. Other causes of hyperglycemia include illness, infection, and post-surgical status.

To further understand hyperglycemia, one must first understand the symptoms of hyperglycemia and how to monitor for such symptoms.

Symptoms of Hyperglycemia

There are various ranges of hyperglycemia, from mild to moderate to severe. Most often, if a person becomes symptomatic of hyperglycemia, their blood sugar is in the moderate or severe range, and they should seek a healthcare provider immediately.

These are the main signs of moderate hyperglycemia:

  • Polyuria (urinating frequently)
  • Polydipsia (excessive thirst and drinking often)
  • Headaches, fatigue, difficulty concentrating
  • Blurred or worsening vision (especially with chronic hyperglycemia)
  • Foot or extremity tingling/pain/numbness/cold insensitivity
  • Slow-healing wounds and skin infections
  • Increased hunger can sometimes occur along with increased thirst


Symptoms of Hyperglycemia

Without treatment, these symptoms will lead to more severe signs of hyperglycemia.

These are the main signs of severe hyperglycemia:

  • Nausea and Vomiting
  • Altered Mental Status
  • Shortness of breath
    • Kussmaul’s breathing (rapid, shallow breaths as a result of diabetic ketoacidosis)
  • Fruity-smelling breath and fruity-smelling urine
  • Excessively high blood sugar upon measurement
  • Ketones in a urine sample
  • Weight loss
  • Abdominal pain and diarrhea
  • Rapid heart beat (tachycardia)
  • Confusion leading to coma

Diabetic Ketoacidosis is a severe, acute state of hyperglycemia that causes the body to go into metabolic acidosis. This means that the blood sugar is so high that the body’s normal acid/base balance is more acidic than usual. Such alterations lead to cellular damage, leading to altered mental status and coma. The body attempts to compensate with Kussmaul breathing, or short, shallow breaths, to push off as much carbon dioxide as possible. DKA is also associated with hypotension, leading to severe hypotension. And this can lead to a state of shock.

DKA is a medical emergency and can be deadly, meaning if you have any signs of DKA or see any signs of DKA in a loved one, then you should call 911 right away. Prolonged severe hyperglycemia can lead to extreme health issues.

Once a person arrives at the hospital to be treated for severe hyperglycemia or diabetic ketoacidosis (DKA), then they are usually treated with intravenous normal saline fluids (IV fluids) and insulin. Once a person starts showing signs of DKA, they should not self-dose insulin until they talk to their healthcare provider. Only with moderate hyperglycemia should a person use insulin on their prescribed sliding scale.

If someone has any concern about their symptoms, they should contact their healthcare provider immediately.

What “numbers” or blood sugar levels indicate hyperglycemia?

Blood sugar is measured through a pinprick of the finger, which draws a bit of blood to be measured in a glucometer.

The measurement for blood sugar is mg/dL.

Blood sugar always increases after a person consumes carbohydrate-based food, therefore, the levels for monitoring for hyperglycemia vary. There is a fasting level (prior to meals) and a casual level (any time during the day, at least 1-2 hours after a meal is consumed).

Fasting Glucose: 

  • High fasting BG > 125 or 130 mg/dL
  • Take this blood glucose measurement with a glucometer at least 8 hours after eating or drinking. Usually the best time to measure fasting glucose is first thing in the morning.
  • Fasting hyperglycemia is usually defined as greater than 125 or 130 mg/dL. However, sometimes  a fasting glucose higher than 100 mg/dL is a sign of mild hyperglycemia, too.

Casual Glucose:

  • High casual BG > 180 mg/dL
  • This blood glucose measurement can be taken at any point throughout the day, but typically after meals (also known as postprandial). The ideal time is 2 hours after a meal.
  • A high casual blood glucose is over 180 mg/dL. Any higher than 180 mg/dL indicates diabetes. Typically a non-diabetic person will almost never have a blood sugar over 140 mg/dL.

Person checking blood sugar levels

Causes of Hyperglycemia


There are numerous potential causes and risk factors for hyperglycemia. So while it is important to be aware of all possible triggers of high blood sugar, it is more important to track and maintain your own symptoms.

The pathophysiology behind high blood sugar is an inability to properly digest and break down carbohydrates. Foods rich in carbohydrates, including bread, fast food, rice, pasta, and pastries, are the most difficult for the body to break down into simple sugars. These foods provide an important energy source called glucose. Glucose is absorbed into the bloodstream as a main energy source, and enters tissue cells with the help of the pancreatic hormone insulin.

Diabetes type 1 and diabetes type 2 both inhibit the ability of the body to use or produce insulin. This impairment prevents the body from properly removing glucose, or sugar, from the blood. Due to such impairment, blood glucose rises to a dangerous level, AKA hyperglycemia, and must be lowered using insulin or other treatments.

Immediate Causes

The most common reasons for an acute hyperglycemia episode are as follows:

  • Lack of medication adherence (forgetting or refusing to use insulin or oral diabetes medications)
  • Expired insulin or improper insulin injection
  • Post-surgery state or having recent surgery
  • Illness and infection (report a fever lasting over 24 hours to your doctor)
  • A recent injury
  • Concurrent medication use, whether that medication is steroids, corticosteroids, or over-the-counter herbs or supplements (check all medications with your doctor)
  • Acute emotional stress or distress
  • Poor eating habits, including a new onset of increased carbohydrate consumption
  • New onset inactivity or poor exercise habits

Risk Factors

There are a few risk factors that make a person more prone to acute hyperglycemia, whether the exacerbation is mild, moderate, or severe.

Past medical history or family history of diabetes mellitus, either type 1 diabetes or type 2 diabetes

If anyone in your family has a history of diabetes, then you have a greater likelihood of developing diabetes, even type 2 diabetes, which typically occurs due to eating and exercise routines.

Obesity or being overweight

These factors alone do not indicate diabetes, however they greatly increase the risk of insulin insufficiency or malfunction which can lead to the development of diabetes and hyperglycemia.

You are of African American, Native American, Hispanic, or Asian American origin

Unfortunately, these ethnoracial groups have increased incidence of both diabetes and hyperglycemia. At this time, there is no singular reason for the increased risk here. There might be a mixture of genetic and socioeconomic factors at play. Yet, there is a clear link between people of these origins and higher risk for hyperglycemia.

You have other medical history, specifically hypertension (high blood pressure) or hyperlipidemia (high cholesterol)

Hypertension is a disease that can lead to blood vessel damage due to high pressure of blood pumping through the arteries and veins. This damage can increase likelihood of insulin insufficiency and blood sugar complications. Similarly, high cholesterol can also damage the vessels by causing blockages or plaques. These both act as risk factors for hyperglycemia.

If you are pregnant, you are diagnosed with gestational diabetes

Most of the time, gestational diabetes is a temporary health issue that causes hyperglycemia and insufficient insulin in pregnant women. This can increase risk of hyperglycemia during the time of pregnancy and antepartum. Occasionally, but rarely, gestational diabetes will last beyond pregnancy as well, leading to further hyperglycemia complications postpartum.

You have an upcoming surgery

Because surgery can increase the likelihood of fluctuating blood glucose levels, having an upcoming surgery can put you at risk for hyperglycemia or hypoglycemia (low blood sugar). However, since you will be in a hospital setting, your blood sugar will be monitored very closely. And any changes that happen in surgery are most likely temporary.

You have a stressful life or work-life balance

Due to stress being an occasional trigger for both hyperglycemia and bad coping habits (overeating or eating junk food), having a constantly stressful day-to-day environment can lead a person to being at more risk for developing hyperglycemia.

When to Go to the Doctor

Call 911 if

  • your blood glucose levels are above 240 mg/dL and you have ketones in your urine
  • you begin to experience confusion or altered mental status
  • you start to have shortness of breath/Kussmaul’s breathing
  • you are too sick (with nausea, vomiting, diarrhea) to keep food or fluids down

Make a doctor’s appointment if

  • You have a fever lasting more than a day or suspected skin/extremity infection
  • You are having persistent nausea, vomiting, or diarrhea, but still keep food/water down
  • You took your Insulin or diabetes medication, but your blood glucose still rises over 240 mg/dL often (or fluctuates from hypoglycemia to hyperglycemia range often)