Causes of Low Blood Sugar Levels (Hypoglycemia)

The body maintains the blood sugar levels within a narrow range between 72 mg/dL (4mmol/L) and 104mg/dL (5.8mmol/L). It is not abnormal for these levels to sometimes rise above 108mg/dL (6mmol/L) or drop as low as 63mg/dL (3.5mmol/L). However, the body’s homeostatic mechanisms and the action of hormones, glucagon and insulin in particular, ensures that there is not a wide fluctuation in the blood glucose levels. In a diabetic, the variations may be significantly large and even reach dangerously high or extremely low levels if proper treatment and management is not implemented.

Low Blood Sugar Levels Causes

Hypoglycemia can be defined according to the presence of the features known as Whipple’s triad. This is often seen in a blood glucose level below 54mg/dL (3mmol/L) in a person who is not diabetic and blood sugar levels below 63mg/dL (3.5mmol/L) in diabetics.

Meals, Fasting and Dieting

  • Eating small amounts of food, missing meals or eating infrequently and waiting for long periods between meals may all cause low blood sugar levels.
  • Strict dieting or fasting often result in severe hypoglycemia. The signs and symptoms of hypoglycemia is not related to any “detoxification” process as claimed by some weight loss and detoxification programs. If left untreated, it can result in serious and even life-threatening complications. Dehydration may also play a part in these cases of hypoglycemia.

Physical Activity and Exercise

  • Strenuous physical activity which is not customary for a person can cause a significant drop in the blood sugar levels, especially if there is inadequate food intake during this period.
  • Exercise which is not a usual practice or unexpectedly excessive may also cause low blood sugar levels.
  • In a person who is accustomed to excessive physical activity and strenuous exercise, the blood sugar levels may not drop to low levels as quickly as in an unfit person. The use of sports drinks may also help to prevent hypoglycemia.


  • Alcohol consumption can increase insulin levels which causes a drop in the blood glucose levels.
  • Diabetics using insulin and other medication that increase insulin production may find that the effect is exacerbated leading to dangerously low blood sugar levels.
  • Consuming small meals before and duringĀ  alcohol intake can reduce this effect. Binge drinking should be avoided.


Hypoglycemia in diabetics may occur as a result of :

  • Excessive and improper use of insulin and other anti-diabetic agents.
  • Increased subcutaneous fat deposits (lipohypertrophy) at injection sites for insulin administration may affect insulin absorption.
  • Alcohol consumption (mentioned above) and drug interactions with other medicines that may affect insulin levels.
  • Breastfeeding by diabetic mothers.

Diabetic patients should be aware of nocturnal hyperinsulinemia as blood glucose levels drop during sleep and incorrect administration of insulin at night could result in hypoglycemia.


  • Hypoglycemia is more likely to occur in infants and the elderly due to poor glucose tolerance.
  • Age is a risk factor rather than a cause of hypoglycemia.

Other Disorders

  • Malabsorption syndromes may affect the absorption of glucose and other nutrients thereby resulting in low blood sugar levels.
  • Conditions that affect normal peristaltic activity like gastroparesis.
  • Hypoglycemia may be a consequence of other disorders like :
    • Addison’s disease
    • Cushing’s syndrome*
    • Pancreatic cancer or other tumors of the pancreas – insulinoma is a tumor of the pancreatic islet cells that secretes insulin.
    • Pituitary insufficiency
    • Liver failure
    • Causes of delayed gastric emptying (gastroparesis, gastric outlet obstruction)

* Cushing’s syndrome usually results in hyperglycemia but acute hypoglycemia attacks may be occur.

Related Articles

  1. What is Low Blood Sugar (Glucose)? Hypoglycemia Range of Levels

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