• Clinical science



Hypoglycemia, or low blood glucose, has many causes, but most commonly occurs in diabetics as a consequence of pharmaceutical diabetes treatment. The onset of hypoglycemic symptoms depends largely on an individual's physiological adaptation mechanisms, although they can start to occur when blood glucose falls below 70 mg/dL. The clinical presentation of hypoglycemia includes autonomic symptoms (i.e., hunger, sweating, tachycardia) and signs of glucose shortage in the brain (i.e., confusion, behavioral changes, somnolence). Since prolonged hypoglycemia can result in acute brain damage, changes in a patient's mental status should prompt immediate measurement of fingerstick blood glucose and treatment. Hypoglycemia treatment in patients who are still conscious consists of a fast-acting carbohydrate such as glucose tablets, candy, or juice. Comatose patients are treated intravenously under continuous plasma glucose monitoring. In order to avoid life-threatening hypoglycemia, diabetic patients must be trained to recognize hypoglycemic symptoms.


The lower limit of normal for fasting plasma glucose is 70 mg/dL (3.9 mmol/L).



Causes of Hypoglycemia
Iatrogenic, excess insulin
Endogenous, excess insulin
  • Chronic alcohol use
Hereditary and acquired conditions


Clinical features

Symptoms of hypoglycemia normally present at approx. 50 mg/dL (2.8 mmol/L); however, this threshold is variable. Low glucose levels may occur during times of fasting, for example, without eliciting symptoms.

Frequent hypoglycemic episodes in diabetics can lead to decreased awareness of the symptoms. In addition, diabetics may miss hypoglycemic warning signs because of autonomic neuropathy! Beta blockers can also mask the signs of hypoglycemia!



General approach

  • Patient history: physical activity; , food intake, alcohol consumption, insulin replacement therapy (units and location of injection) and other medications
  • Laboratory tests:
    • ↓ Blood glucose or self-monitored blood glucose (SMBG)
    • Sulfonylurea level and exogenous insulin (elevated insulin with low C-peptide)
      • Helpful in cases of suspected factitious hypoglycemia
        • If factitious disorder is suspected, it is important to build a strong doctor-patient relationship, and to confront the patient about surreptitious insulin or sulfonylurea use in a nonthreatening manner

In diabetic patients

  • Concern is warranted at SMBG levels < 70 mg/dL (3.9 mmol/L).

In non‑diabetic patients

Fingerstick blood glucose should be checked in every emergency situation involving altered mental status!

  • Non‑diabetic patients should be assessed for a hypoglycemic disorder (especially insulinoma!) if they meet the criteria of Whipple's triad:
    1. Symptoms of hypoglycemia (see "Clinical features" above)
    2. Concomitant low plasma glucose
    3. Relief of symptoms after administering glucose
  • Glucose levels < 50 mg/dL (2.2 mmol/L) should also prompt further investigation, even if they are asymptomatic.



  • Patient is conscious: oral glucose 15–20 g or fast-acting carbohydrates such as glucose tablets, candy, or juice
  • Patient is unconscious (or unable to ingest glucose)
    • In the hospital: 25 g of 50% glucose IV (dextrose) and regular serum glucose monitoring. Subsequent glucose infusions or food may be needed.
  • If both oral and IV routes are not feasible: 0.5–1.0 mg glucagon IM or SC

Suspected hypoglycemia should be treated immediately without waiting for the results of blood glucose testing!


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last updated 01/27/2020
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