Blood Sugar

Our body breaks down every carb we ingest into glucose, also known as blood sugar because it travels through our bloodstream. Glucose is a simple sugar — more precisely, a monosaccharide (mono meaning single and saccharide meaning sugar).

To store glucose, your body combines the molecules into a polysaccharide (poly meaning several) called glycogen, which gets stored in our liver and muscles.

Insulin (a hormone produced by our pancreas) rises when blood glucose rises; it lowers blood sugar by telling various cells to absorb it — for storage in our liver or muscles or for immediate use — and our liver to stop producing new glucose.

The ability of cells to absorb glucose in response to insulin is called insulin sensitivity, and low insulin sensitivity is called insulin resistance. The more sensitive we are to insulin, the less resistant, and vice versa.

It is also possible to produce too little insulin. If we have type 1 diabetes or are in the late stages of type 2 diabetes, in which case we suffer from insulin deficiency, glucose can’t be removed efficiently from our blood, causing hyperglycemia (overly high glucose levels).

Insulin resistance paves the way for type 2 diabetes, which can cause our blood sugar levels to consistently remain too high for too long. If not managed, these high blood sugar levels can lead to serious health complications — mostly cardiovascular diseases, but probably cancer, Alzheimer’s, and Parkinson’s as well.

How are blood glucose levels assessed?

Glycemic control can be tested several ways, each with its own cutoff values indicating impaired glucose regulation. Of these tests, fasting blood glucose is the most common, followed by hemoglobin A1C (HbA1c).

Fasting Plasma Glucose

Fasting plasma glucose (FPG), also known as fasting blood glucose, is simply a measure of how much glucose is floating around in your blood during a fast. After at least 8 hours of not eating (typically in the morning, before breakfast), blood is drawn and analyzed for glucose concentration.

Interpreting FPG results


<5.6 (mmol/L)


5.6–7.0 (mmol/L)


>7.0 (mmol/L)

Hemoglobin A1c

Hemoglobin A1c (HbA1c), or glycated hemoglobin, is a marker of blood-glucose metabolism that estimates the average amount of glucose in your blood over the past 3 months.

The protein that carries oxygen throughout your body, called hemoglobin, is in red blood cells, which live for about 4 months. Glycation is when a sugar — in this case, glucose — is linked to a protein or lipid — in this case, hemoglobin. When blood glucose levels rise, the rate of hemoglobin glycation increases, making glycated hemoglobin an estimate of blood glucose levels over months.

Interpreting HbA1c results


<5.7 (mmol/L)


5.7–6.4 (mmol/L)


≥6.5 (mmol/L)

What are the symptoms of abnormal blood glucose levels?

Symptoms of abnormal glucose levels are different from person to person and may not even be present until the levels are very high or very low. Generally, blood sugar symptoms may show up when levels fall below (3.9 mmol/L) or over (10 mmol/L).

Symptoms of high and low blood glucose


Anxiety Blurred vision Changes in behavior or personality Clammy skin Confusion Difficulty speaking Disorientation Dizziness or lightheadedness Fast or irregular heartbeat Fatigue Feeling shaky or jittery Headache Hunger Lacking coordination Nausea Seizure Sleepiness Sweating Weakness


Blurry vision Dry mouth Dry skin Fatigue Frequent urination Fruity breath odor Increased thirst Nausea and vomiting Rapid heartbeat Shortness of breath Stomach pain