What are causes of low blood sugar?

Updated at: Jan 22, 2013
What are causes of low blood sugar?
Dr Poonam Sachdev
Other DiseasesWritten by: Dr Poonam SachdevPublished at: Jan 22, 2013

A single episode of low blood sugar is not alarming and does not need to be evaluated. But repeated episodes of documented hypoglycemia in people not on medications to treat diabetes needs to be evaluated carefully by an endocrinologist. If you have repeated episodes of low blood sugar or chronic hypoglycemia, your body loses it’s ability to respond vigorously to low blood sugar. Some common causes of low blood sugar or hypoglycemia are;

  • In people with diabetes overmedication with insulin or other oral anti-diabetic medications
  • Certain medications can cause hypoglycemia such as beta blockers, pentamidine, and sulfamethoxazole and trimethoprim.
  • Excessive use of alcohol
  • Missed meals or if you remain hungry for prolonged period
  • Severe infection (sepsis)
  • Poor oral intake due to infection, any chronic disease like cancer
  • Endocrinal disease like adrenal insufficiency
  • Kidney or liver failure
  • Inborn error or congenital, genetic defects of insulin release and blood glucose metabolism (congenital hyperinsulinism)
  • Certain conditions that can increase insulin release (like infant born to a diabetic mother, birth trauma, reduced oxygen delivery during birth, Beckwith-Wiedemann syndrome, and certain rarer genetic conditions)
  • Tumors of insulin-producing cells (Insulinoma or insulin-producing tumor)
  • Certain other tumors such as hepatoma, mesothelioma, and fibrosarcoma (these tumors may produce insulin-like factors which can lead to hypoglycemia) If you have repeated episodes of symptoms suggestive of low blood sugar consult your doctor.


Understanding Normal Glucose Levels? It is important for people with diabetes to monitor their blood sugar levels. Glucose is the type of simple sugar that the cells use for energy. In people with diabetes blood glucose levels is elevated. Blood sugar test is done to measure the amount glucose, present in your blood. Your doctor may recommend measurement of;

  • Fasting blood glucose (done in the morning before you eat or drink anything even tea or coffee).
  • Randomblood glucose (done at any time of the day)
  • Post-prandial blood glucose (is done 2 hours after eating)


The results of these tests are mostly ready in 1 to 2 hours. To measure the amount of glucose present in your blood---blood is drawn from a vein. Blood is usually drawn from the veins present inside the elbow or on the back of the hand. The reading on doing glucose level testing by blood sample taken from your vein (called a blood plasma value) and checked by finger prick test can differ a little. Normal blood glucose levels;

  • Fasting blood glucose:70-99 milligrams per deciliter (3.9-5.5 mmol/L)
  • 2 hours after eating (postprandial):70-145 mg/dL (3.9-8.1 mmol/L)
  • Random blood sugar:70-125 mg/dL (3.9-6.9 mmol/L)


The results of blood sugar levels can vary slightly from lab to lab. Blood sugar levels can be affected by many conditions. The most common cause of high blood sugar is diabetes. If your blood sugar levels are elevated your doctor may recommend re-testing of sugar levels and if required other tests. DO not ignore if your blood test results are abnormal.



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