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Hypoglycemia (Low Blood Sugar)

Last Updated on Nov 30, 2019
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What is Hypoglycemia?

Hypoglycemia or low blood sugar in diabetic patients is a paradox since diabetes is characterized by high glucose levels in the blood. However, diabetics on insulin or certain oral hypoglycemic drugs can suffer from low blood sugar.


This usually happens if the patient has taken a higher than normal dose of insulin or oral medication, if the patient has skipped a meal or has undergone excessive physical activity. Patients with type 1 diabetes are particularly prone to hypoglycemic episodes.

Glucose Maintenance in the Body

Normal glucose levels in the body is between 70 to 110 mg/dL in a fasting state. This is maintained by a careful balance between several hormones, mainly insulin and glucagon. If the blood glucose levels are high, the pancreas secretes insulin, which acts to reduce the blood glucose level. On the other hand, if the level of glucose falls below normal, the pancreas reduces the secretion of insulin and later increases the secretion of glucagon. Glucagon increases the glucose level by increasing its production by the liver. If for some reason the glucagon is insufficient, epinephrine is released by the body to increase the blood glucose level. Blood glucose levels in the body is maintained through a balance of insulin-glucagon production.

How to Identify Hypoglycemia?

Diagnosis of hypoglycemia is made based on the Whipple’s triad. Accordingly, three characteristics should be present to label a patient as suffering from hypoglycemia:

  • Presence of symptoms consistent with hypoglycemia
  • Low plasma glucose level that has been accurately measured
  • Reversal of symptoms after increasing the plasma glucose levels with treatment

Symptoms consistent with hypoglycemia include the following:

  • Neurological symptoms: Since the brain needs a continuous supply glucose, a drop in blood glucose produces symptoms like confusion, loss of consciousness and even seizures.
  • Some non-specific symptoms alert the person that the blood glucose levels are likely to be low. These symptoms include irritability, palpitations, tremor, anxiety, sweating and hunger. These effects of low blood sugar are mediated by the autonomic nervous system. It must be remembered that a complication of diabetes is neuropathy, where nerves are affected. Thus, if the autonomic nerves are affected, these warning signs may not occur. This condition is referred to as “hypoglycemia unawareness”.

What are the Causes of Hypoglycemia?

Causes of hypoglycemia in a patient with diabetes include:

  • Excessive dose of insulin or oral hypoglycemic drug
  • Exercising more than usual which burns calories faster
  • Skipping a meal or not taking meals on time
  • Following intake of alcohol
  • Failure to adjust the dose of medication after introducing lifestyle changes or achieving weight loss
  • Decreased kidney function, which results in reduced elimination of insulin from the body. This results in higher-than-normal insulin levels in patients taking insulin treatment, which causes hypoglycemia.

Though most cases of hypoglycemia occur in patients who are diabetics on treatment, hypoglycemia can also occur in patients without diabetes. Some of the other causes of hypoglycemia include:

  • Intake of drugs which include beta-blockers, quinine, indomethacin and sulphonamides
  • Severe liver, kidney or heart disease
  • Blood infection called sepsis
  • Intake of alcohol over several days along with reduced food intake
  • Starvation
  • Hormone deficiencies like growth hormone and cortisol deficiency
  • Presence of tumors including those of liver or adrenal gland, insulin-secreting tumors called insulinomas or tumors secreting certain hormones called carcinoid tumors.

How to Diagnose Hypoglycemia?

Hypoglycemia is diagnosed based on the following features:

  • Symptoms of palpitations, sweating, confusion etc. with a blood test showing low blood glucose levels. Hypoglycemia should be suspected in a diabetes patient with severe neurological symptoms including coma.
  • Relief of symptoms on the administration of glucose helps to confirm the diagnosis.
  • In cases where the cause of hypoglycemia cannot be established, additional blood tests like measurement of insulin, proinsulin, C-peptide and beta-hydroxybutyrate assist in the diagnosis. Higher than normal insulin, proinsulin and C-peptide values, and lower beta-hydroxybutyrate levels may indicate excess insulin levels in the body.

What are the Treatments for Hypoglycemia?

If hypoglycemia is left untreated for a prolonged duration, it can cause permanent brain damage. Therefore, treating low blood sugar should be considered an emergency. Immediate treatment of hypoglycemia involves the use of oral glucose or sugar or candy, whichever is available at hand. If the patient cannot take glucose orally, the glucose can be administered through an intravenous injection. Glucagon is effective when given as an intramuscular or subcutaneous injection in patients with type 1 diabetes. The cause of hypoglycemia should also be identified and treated, for example with dosage adjustment, to bring about control of blood sugars and prevent similar episodes in the future.

How to Prevent Hypoglycemia?

Episodes of hypoglycemia should be avoided as far as possible. Some steps to prevent hypoglycemia in diabetes patients include:

  • Check blood sugar levels on a regular basis and adjust your medications to avoid hypoglycemia.
  • Understand the common symptoms of hypoglycemia, and reach for help if you recognize any of them.
  • Take extra precautions in situations that are likely to cause hypoglycemia, for example, if you are ill or are likely to exercise more than normal.
  • Eat food at regular intervals. Do not skip meals. A dietician could be helpful in planning out a meal schedule that can avoid hypoglycemia.
  • Avoid intake of alcohol, especially on an empty stomach.
  • Always carry a card mentioning that you are a diabetic along with the medications you take. This information will be useful if you suddenly fall unconscious due to hypoglycemia.
  1. Low Blood Glucose (Hypoglycemia) - (http://www.niddk.nih.gov/health-information/health-topics/Diabetes/hypoglycemia/Pages/index.aspx)
  2. Hypoglycemia - (http://www.mayoclinic.org/diseases-conditions/diabetes/expert-blog/hypoglycemia-unawareness/bgp-20056549)
  3. Kasper, D., Fauci, A., Hauser, S., Longo, J., Jameson, J., et.al. (2015). Harrison's Principles of Internal Medicine 19th Edition. (Vol. 1 & Vol. 2). McGraw Hill Professional.

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