Last updated: September 20, 2023

Summarytoggle arrow icon

Hypoglycemia, or low blood sugar, has a variety of causes, but most often occurs as a result of insulin therapy or other medications in patients with diabetes. Although hypoglycemic symptoms can appear when blood glucose is < 70 mg/dL, its onset depends largely on individual physiological adaptation mechanisms. Hypoglycemia manifests with autonomic symptoms such as hunger, sweating, and tachycardia, as well as neuroglycopenic symptoms such as confusion, behavioral changes, and somnolence. A change in a patient's mental status should prompt immediate fingerstick blood glucose measurement and treatment if needed, as prolonged hypoglycemia can potentially cause acute brain damage. Glucose is the preferred treatment. Patients who are conscious should receive a fast-acting carbohydrate such as glucose tablets, candy, or fruit juice. Intravenous dextrose or intramuscular glucagon is administered to unresponsive patients.

Definitiontoggle arrow icon

The following is consistent with the 2021 American Diabetes Association guidance. [1]

  • Hypoglycemia in patients with diabetes: generally described as 70 mg/dL (≤ 3.9 mmol/L) [1][2]
    • Level 1: blood glucose level of 54–70 mg/dL
    • Level 2: blood glucose level < 54 mg/dL
    • Level 3: hypoglycemia episode with altered mental status or physical impairment requiring assistance to treat
  • Hypoglycemia in patients without diabetes: blood glucose level < 55 mg/dL with symptoms of hypoglycemia [3]
  • Whipple triad: helps to confirm the diagnosis of hypoglycemia [4][5]
    • Low blood glucose levels
    • Signs or symptoms consistent with hypoglycemia (see “Clinical features”)
    • Relief of symptoms when blood glucose increases after treatment

Etiologytoggle arrow icon

Diabetic patients [5][6]

Causes of hypoglycemia in patients with diabetes
Acute illness

In patients with diabetes who present with hypoglycemia in the absence of medication changes, consider another underlying condition, e.g., acute infection or decreased drug metabolism or drug excretion secondary to new-onset organ impairment. [11]

(Relative) overdose of insulin or a noninsulin drug is by far the most common cause of hypoglycemia.

Consider factitious disorder in patients with access to insulin and other diabetes medications (e.g., healthcare professionals), for whom there is no other obvious explanation for hypoglycemia.

Nondiabetic patients [5][6]

Causes of hypoglycemia in patients without diabetes
Critical illness
Drugs that cause hypoglycemia [6]
Hormone deficiencies
Endogenous hyperinsulinism
Exogenous hyperinsulinism
Genetic and congenital disorders [12]

Older patients are at risk of developing hypoglycemia regardless of diabetes status, and they are at increased risk of adverse outcomes resulting from hypoglycemic episodes. [13]

Clinical featurestoggle arrow icon

Threshold for symptoms

  • Varies greatly; , but most adults become symptomatic when blood glucose level is less than approx. 50 mg/dL (2.8 mmol/L)
  • The threshold of symptoms is especially variable in individuals with type 1 diabetes and those with longstanding type 2 diabetes due to hypoglycemia-associated autonomic failure (HAAF). [4]
    • Recurrent hypoglycemia → changes in the counterregulatory autonomic response (e.g., decreased epinephrine release) → lower glucose threshold needed to trigger symptoms → asymptomatic hypoglycemia
    • The initial symptom of hypoglycemia in patients with HAAF is often confusion.
  • Can also vary due to medication: Beta blockers can mask signs of hypoglycemia.

Educating patients about hypoglycemia unawareness can help them to recognize the onset of autonomic symptoms and minimize the risk of severe hypoglycemia.

Signs and symptoms

Beta blockers can mask signs of hypoglycemia.

Hypoglycemia is rare in patients without diabetes and should prompt investigation for an underlying hypoglycemic disorder. [5]

Managementtoggle arrow icon

In unstable patients with suspected hypoglycemia, obtain POC glucose and treat symptomatic patients without delay.

Initial management [2][5][14][15]

Check POC glucose routinely for patients with unexplained AMS or coma, or other clinical features of hypoglycemia. Treat suspected severe hypoglycemia immediately, without waiting for confirmatory testing!

Subsequent management

If there is an inadequate response to parenteral glucose treatment, consider other causes of hypoglycemia, e.g., sepsis, toxin ingestion, hepatic failure, or adrenal insufficiency.

Disposition [2][11][14]

Disposition is variable and depends on multiple factors, e.g., the response to treatment, presence of comorbidities, the cause of hypoglycemia, and other patient factors such as social determinants of health. Follow local protocols and consult a specialist when available.

  • Admission
    • Consider ICU admission with hourly glucose monitoring if hypoglycemia is refractory.
    • Consider ward admission for patients with any of the following:
      • Hypoglycemia secondary to sulfonylurea and long-acting insulin overdose
      • Neuroglycopenic symptoms that do not rapidly improve with glucose treatment
      • Outpatient workup to diagnose the underlying cause of hypoglycemia in nondiabetic patients is not feasible.
      • Inability to tolerate oral food or liquid intake
      • Intentional overdose with insulin or sulfonylurea
  • Discharge (after an uneventful 4-hour monitoring period)
    • Consider discharge home for reliable patients who have social support and any of the following clinical syndromes:
      • Type 1 diabetes mellitus with a short episode of hypoglycemia
      • An isolated episode of unintentional hypoglycemia
    • Discharge planning
      • Educate patients on prescribed medications, self-monitoring, patient safety measures , and reasons to return to seek care, e.g., recurrent symptoms of hypoglycemia. [17]
      • Ensure follow-up with primary care provider or clinical diabetes specialist as needed.

Diagnosticstoggle arrow icon


  • Confirm low blood glucose (via fingerstick or BMP) and check for Whipple triad.
  • Investigate any acute illness as a cause (e.g., infection, sepsis, burns).
  • Review medications (see “Drugs that cause hypoglycemia”).
  • Perform diagnostic workup based on the leading differential diagnosis and whether the patient has diabetes.

Further workup for hypoglycemia is usually only indicated if all features of the Whipple triad are present. [16]

Do not delay treatment of symptomatic hypoglycemia in favor of formally testing for blood glucose levels (see “Management”).

Patients with diabetes [4]

Patients without diabetes [5]

Nonsuppressed serum insulin concentrations with decreased serum C-peptide and proinsulin concentrations are consistent with exogenous insulin use.

Differential diagnosestoggle arrow icon

The differential diagnosis of hypoglycemia is broad because of nonspecific symptoms, and the condition may be diagnosed incorrectly as a neurological, psychiatric, or cardiovascular disorder. [11]

Always consider hypoglycemia in the differential diagnosis of altered mental status.

The differential diagnoses listed here are not exhaustive.

Treatmenttoggle arrow icon

Reversing hypoglycemia

Monitor patients regularly for rebound hypoglycemia after treatment.

  • Alert and oriented patients
    • Oral glucose 15–20 g [14]
    • Fast-acting carbohydrates (e.g., glucose tablets, candy, or fruit juice) [14]
  • Patients with altered mental status (or impaired oral intake) [5]
    • IV dextrose (e.g., D50W): Repeat after 15 minutes if hypoglycemia persists; multiple doses may be required. [11][14]
    • IM glucagon: if neither oral nor IV routes of administering glucose are feasible [14]

For patients with type 1 diabetes presenting with hypoglycemia and using insulin pumps, do not discontinue insulin pumps and treat hypoglycemia as usual. Removing the insulin pump puts patients at risk for diabetic ketoacidosis. [11]

Avoid giving orange juice to patients with CKD on a low-potassium diet as it is high in potassium. [14]

Adjunctive therapy

Treatment of the underlying causes

Acute management checklisttoggle arrow icon

  • Confirm hypoglycemia (if patient is stable enough).
  • Treat suspected hypoglycemia with oral glucose, IV dextrose, or IM glucagon.
  • Recheck glucose after 15 minutes and repeat treatment as needed.
  • Start dextrose infusion if hypoglycemia is refractory.
  • Check C-peptide and insulin antibodies if there is concern for medication overdose.
  • Rule out acute illness as the cause.
  • Rule out medications as the cause.
  • Consider further diagnostic workup if no clear cause is identified.
  • Consider endocrinology consult.
  • Consider ICU admission if the patient is critically ill or requires hourly glucose monitoring and a dextrose infusion.

Complicationstoggle arrow icon

Acute complications of untreated hypoglycemia [13][14]

Chronic complications of recurrent hypoglycemia [13][14]

These are particularly pronounced in older adults.

We list the most important complications. The selection is not exhaustive.

Referencestoggle arrow icon

  1. American Diabetes Association Professional Practice Committee. 6. Glycemic Targets: Standards of Medical Care in Diabetes—2022. Diabetes Care. 2021; 45 (Supplement_1): p.S83-S96.doi: 10.2337/dc22-s006 . | Open in Read by QxMD
  2. Walls R, Hockberger R, Gausche-Hill M. Rosen's Emergency Medicine. Elsevier Health Sciences ; 2018
  3. Kandaswamy L, Raghavan R, Pappachan JM. Spontaneous hypoglycemia: diagnostic evaluation and management. Endocrine. 2016; 53 (1): p.47-57.doi: 10.1007/s12020-016-0902-0 . | Open in Read by QxMD
  4. Seaquist ER, Anderson J, Childs B, et al. Hypoglycemia and diabetes: a report of a workgroup of the American Diabetes Association and The Endocrine Society. Diabetes Care. 2013; 36 (5): p.1384-1395.doi: 10.2337/dc12-2480 . | Open in Read by QxMD
  5. Cryer et al.. Evaluation and Management of Adult Hypoglycemic Disorders: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2009; 94 (3): p.709-728.doi: 10.1210/jc.2008-1410 . | Open in Read by QxMD
  6. Desimone et al.. Non-Diabetic Hypoglycemia. Endotext. 2000.
  7. Sarkar U, Karter AJ, Liu JY, Moffet HH, Adler NE, Schillinger D. Hypoglycemia is More Common Among Type 2 Diabetes Patients with Limited Health Literacy: The Diabetes Study of Northern California (DISTANCE). J Gen Intern Med. 2010; 25 (9): p.962-968.doi: 10.1007/s11606-010-1389-7 . | Open in Read by QxMD
  8. Seligman HK, Davis TC, Schillinger D, Wolf MS. Food insecurity is associated with hypoglycemia and poor diabetes self-management in a low-income sample with diabetes.. J Health Care Poor Underserved. 2010; 21 (4): p.1227-33.doi: 10.1353/hpu.2010.0921 . | Open in Read by QxMD
  9. Lin YK, Hung M, Sharma A, et al. Impaired Awareness of Hypoglycemia Continues to be a Risk Factor for Severe Hypoglycemia Despite the Use of Continuous Glucose Monitoring System in Type 1 Diabetes. Endocr Prac.. 2019; 25 (6): p.517-525.doi: 10.4158/ep-2018-0527 . | Open in Read by QxMD
  10. Silbert R, Salcido-Montenegro A, Rodriguez-Gutierrez R, Katabi A, McCoy RG. Hypoglycemia Among Patients with Type 2 Diabetes: Epidemiology, Risk Factors, and Prevention Strategies. Curr Diab Rep. 2018; 18 (8).doi: 10.1007/s11892-018-1018-0 . | Open in Read by QxMD
  11. Tintinalli JE, Stapczynski JS, Ma OJ, Yealy D, Meckler GD, Cline DM. Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 9th edition. McGraw Hill Professional ; 2019
  12. Fabian Yap SC. Genetic Disorders Leading to Hypoglycaemia. Journal of Genetic Syndromes & Gene Therapy. 2013; 04 (10).doi: 10.4172/2157-7412.1000192 . | Open in Read by QxMD
  13. Abdelhafiz AH, Rodríguez-Mañas L, Morley JE, Sinclair AJ. Hypoglycemia in Older People - A Less Well Recognized Risk Factor for Frailty. Aging Dis.. 2015; 6 (2): p.156.doi: 10.14336/ad.2014.0330 . | Open in Read by QxMD
  14. Ng CL. Hypoglycaemia in nondiabetic patients - an evidence.. Aust Fam Physician. 2010; 39 (6): p.399-404.
  15. Tomky D. Detection, prevention, and treatment of hypoglycemia in the hospital. Diabetes Spectr. 2005; 18 (1): p.39-44.doi: 10.2337/diaspect.18.1.39 . | Open in Read by QxMD
  16. Principi T, Schonfeld D, Weingarten L, Schneeweiss S, Rosenfield D, Ernst G, Schuh S, Scolnik D. Update in Pediatric Emergency Medicine: Pediatric Resuscitation, Pediatric Sepsis, Interfacility Transport of the Pediatric Patient, Pain and sedation in the Emergency Department, Pediatric Trauma. Springer International Publishing ; 2018: p. 223-249
  17. Ghosh A, Banerjee I, Morris AAM. Recognition, assessment and management of hypoglycaemia in childhood. Arch Dis Child. 2015; 101 (6): p.575-580.doi: 10.1136/archdischild-2015-308337 . | Open in Read by QxMD
  18. Alvanzo et al.. The ASAM Clinical Practice Guideline on Alcohol Withdrawal Management. Journal of Addiction Medicine. 2020; 14 (3S): p.1-72.doi: 10.1097/adm.0000000000000668 . | Open in Read by QxMD
  19. American Diabetes Association. Diabetes and Driving. Diabetes Care. 2013; 37 (Supplement_1): p.S97-S103.doi: 10.2337/dc14-s097 . | Open in Read by QxMD
  20. Emanuele NV, Swade TF, Emanuele MA. Consequences of Alcohol Use in Diabetics. Alcohol Health Res World. 1998; 22 (3): p.211-219.
  21. Service FJ, Cryer PE. Hypoglycemia in adults: Clinical manifestations, definition, and causes. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. Last updated: June 16, 2015. Accessed: February 14, 2017.
  22. Hypoglycemia Diagnosis, A three-step approach: Whipple's Triad. Updated: May 10, 2014. Accessed: February 14, 2017.

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