Basic Metabolic Panel: Difference between revisions

(Created page with "==Background== The '''Basic Metabolic Panel''' (BMP) is a standard diagnostic test used to evaluate fluid balance, electrolyte status, and renal function. It typically includes measurements of sodium, potassium, chloride, bicarbonate, blood urea nitrogen (BUN), creatinine, and glucose.<ref name="pmid32443130">Bertschi LA. Abnormal Basic Metabolic Panel Findings: Implications for Nursing. Am J Nurs. 2020 Jun;120(6):48-55. [https://pubmed.ncbi.nlm.nih.gov/32443130/ PubMed...")
 
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==Background==
==Background==
The '''Basic Metabolic Panel''' (BMP) is a standard diagnostic test used to evaluate fluid balance, electrolyte status, and renal function. It typically includes measurements of sodium, potassium, chloride, bicarbonate, blood urea nitrogen (BUN), creatinine, and glucose.<ref name="pmid32443130">Bertschi LA. Abnormal Basic Metabolic Panel Findings: Implications for Nursing. Am J Nurs. 2020 Jun;120(6):48-55. [https://pubmed.ncbi.nlm.nih.gov/32443130/ PubMed Abstract]</ref>
The '''Basic Metabolic Panel''' (BMP), often referred to as a '''Chem-7''' or '''SMA-7''', is one of the most frequently ordered laboratory tests in the Emergency Department. It provides a rapid assessment of fluid status, electrolytes, renal function, and glucose levels.<ref name="pmid32443130">Bertschi LA. Abnormal Basic Metabolic Panel Findings: Implications for Nursing. Am J Nurs. 2020 Jun;120(6):48-55. [https://pubmed.ncbi.nlm.nih.gov/32443130/ PubMed Abstract]</ref>


When [[calcium]] is included, the panel is often referred to as a "Chem-8." Interpretation of these values allows for the rapid identification of metabolic abnormalities, renal failure, and diabetic emergencies.<ref name="pmid29858101">Kildow BJ et al. The Utility of Basic Metabolic Panel Tests After Total Joint Arthroplasty. J Arthroplasty. 2018 Sep;33(9):2752-2758. [https://pubmed.ncbi.nlm.nih.gov/29858101/ PubMed Abstract]</ref>
Including [[Calcium]] technically makes the panel a '''Chem-8'''. It differs from the [[Comprehensive Metabolic Panel]] (CMP) by the lack of [[Liver Function Tests]] (LFTs).


==Components and Interpretation==
==Components and Reference Ranges==
''Reference ranges vary by laboratory. Typical adult values are listed below.''<ref name="pmid25295502">Berend K, de Vries AP, GansRO. Physiological approach to assessment of acid-base disturbances. N Engl J Med. 2014 Oct 9;371(15):1434-45. [https://pubmed.ncbi.nlm.nih.gov/25295502/ PubMed Abstract]</ref>
 
{| class="wikitable"
! Component !! Abbreviation !! Normal Range (US) !! SI Units
|-
| [[Has LabTest::Sodium]] || Na || 135 – 145 mEq/L || 135 – 145 mmol/L
|-
| [[Has LabTest::Potassium]] || K || 3.5 – 5.0 mEq/L || 3.5 – 5.0 mmol/L
|-
| [[Has LabTest::Chloride]] || Cl || 95 – 105 mEq/L || 95 – 105 mmol/L
|-
| [[Has LabTest::Bicarbonate]] (Total CO2) || HCO3 / CO2 || 22 – 29 mEq/L || 22 – 29 mmol/L
|-
| [[Has LabTest::Blood Urea Nitrogen]] || BUN || 7 – 20 mg/dL || 2.5 – 7.1 mmol/L
|-
| [[Has LabTest::Creatinine]] || Cr || 0.6 – 1.2 mg/dL || 53 – 106 µmol/L
|-
| [[Has LabTest::Glucose]] || Glu || 70 – 100 mg/dL (fasting) || 3.9 – 5.6 mmol/L
|-
| [[Has LabTest::Calcium]] || Ca || 8.5 – 10.2 mg/dL || 2.1 – 2.6 mmol/L
|}
 
==Interpretation==


===Sodium (Na)===
===Sodium (Na)===
* '''Normal Range:''' 135–145 mEq/L
* '''[[Hyponatremia]] (<135):'''
* '''[[Hyponatremia]] (<135):'''
** Evaluate volume status (hypovolemic, euvolemic, hypervolemic).
** <120 mEq/L is a critical value (Risk of [[Seizure]], coma).<ref name="pmid10816188">Adrogué HJ, Madias NE. Hyponatremia. N Engl J Med. 2000 May 25;342(21):1581-9. [https://pubmed.ncbi.nlm.nih.gov/10816188/ PubMed Abstract]</ref>
** Monitor for neurological sequelae (seizure, coma) if drop is acute or severe (<120 mEq/L).
** Assess volume status (Hypovolemic, Euvolemic, Hypervolemic).
** ''Pearls:'' rule out Pseudohyponatremia (Hyperlipidemia/Hyperproteinemia) and Hyperglycemic induced (Corrected Na = Measured Na + 1.6 * [(Glucose - 100) / 100]).<ref name="pmid10225241">Hillier TA, Abbott RD, Barrett EJ. Hyponatremia: evaluating the correction factor for hyperglycemia. Am J Med. 1999 Apr;106(4):399-403. [https://pubmed.ncbi.nlm.nih.gov/10225241/ PubMed Abstract]</ref>
* '''[[Hypernatremia]] (>145):'''
* '''[[Hypernatremia]] (>145):'''
** Indicates free water deficit relative to sodium.
** Almost always implies free water deficit ([[Dehydration]]).
** Associated with dehydration or diabetes insipidus.
** Calculate Free Water Deficit.


===Potassium (K)===
===Potassium (K)===
* '''Normal Range:''' 3.5–5.0 mEq/L
* '''[[Hyperkalemia]] (>5.0):'''
* '''[[Hyperkalemia]] (>5.0):'''
** ''Emergency:'' Values >6.0 mEq/L or ECG changes (peaked T waves, QRS widening) require immediate calcium stabilization and shifting agents (insulin/dextrose).<ref name="pmid22413702">Pepin J, Shields C. Advances in diagnosis and management of hypokalemic and hyperkalemic emergencies. Emerg Med Pract. 2012 Feb;14(2):1-17. [https://pubmed.ncbi.nlm.nih.gov/22413702/ PubMed Abstract]</ref>
** ''Emergency:'' >6.0 or any ECG changes ([[Peaked T waves]], QRS widening, Sine wave).
** Common etiologies: Renal failure, acidosis, hemolysis (pseudohyperkalemia), or medications.<ref name="pmid9167648">Mandal AK. Hypokalemia and hyperkalemia. Med Clin North Am. 1997 May;81(3):611-39. [https://pubmed.ncbi.nlm.nih.gov/9167648/ PubMed Abstract]</ref>
** Causes: [[Renal Failure]], [[Rhabdomyolysis]], missed dialysis, [[Acidosis]] (shifts K out of cells), [[Hemolysis]] (lab error).<ref name="pmid18272089">Montague BT, Ouellette JR, Buller GK. Retrospective review of the frequency of ECG changes in hyperkalemia. Clin J Am Soc Nephrol. 2008 Mar;3(2):324-30. [https://pubmed.ncbi.nlm.nih.gov/18272089/ PubMed Abstract]</ref>
* '''[[Hypokalemia]] (<3.5):'''
* '''[[Hypokalemia]] (<3.5):'''
** ''Emergency:'' Risk of arrhythmias and respiratory muscle weakness.
** Causes: Diuretics, GI loss (diarrhea/vomiting).
** Common etiologies: GI losses (vomiting/diarrhea), diuretics, or intracellular shifts.<ref name="pmid24139581">Daly K, Farrington E. Hypokalemia and hyperkalemia in infants and children: pathophysiology and treatment. J Pediatr Health Care. 2013 Nov-Dec;27(6):486-96. [https://pubmed.ncbi.nlm.nih.gov/24139581/ PubMed Abstract]</ref>
** ''Emergency:'' Arrhythmias, U-waves, respiratory muscle weakness.
** Always check and replete [[Magnesium]] with K.


===Chloride (Cl)===
===Chloride (Cl)===
* '''Normal Range:''' 95–105 mEq/L
* Generally follows Sodium status.
* Primarily used to assess acid-base status and anion gap.
* '''Hyperchloremia:''' Often iatrogenic from large volume [[Normal saline]] resuscitation (Non-gap metabolic acidosis).
* '''Hyperchloremia:''' Often associated with aggressive normal saline resuscitation (non-gap metabolic acidosis).
* '''Hypochloremia:''' Gastric outlet obstruction/vomiting (Metabolic alkalosis).<ref name="pmid25295502" />
* '''Hypochloremia:''' Associated with metabolic alkalosis (e.g., vomiting, gastric suction).<ref name="pmid714831">Burke MD. Electrolyte studies. 2. Potassium, chloride, and acid-base. Postgrad Med. 1978 Nov;64(5):205-12. [https://pubmed.ncbi.nlm.nih.gov/714831/ PubMed Abstract]</ref>


===Bicarbonate (CO2)===
===Bicarbonate (CO2)===
* '''Normal Range:''' 22–29 mEq/L
* Represents total venous CO2 content (mostly HCO3).
* Measures total venous CO2 content, serving as a proxy for serum bicarbonate.
* '''Low (<22):''' [[Metabolic Acidosis]] (most common in ED) or compensation for respiratory alkalosis.
* '''Low (<22):''' Suggests [[Metabolic Acidosis]] (calculate Anion Gap) or respiratory alkalosis compensation.<ref name="pmid22237220">Sotirakopoulos N et al. Acid-base and electrolyte disorders in patients with diabetes mellitus. Saudi J Kidney Dis Transpl. 2012 Jan;23(1):58-62. [https://pubmed.ncbi.nlm.nih.gov/22237220/ PubMed Abstract]</ref>
** Calculate [[Anion Gap]] (see below).
* '''High (>29):''' Suggests [[Metabolic Alkalosis]] or respiratory acidosis compensation (e.g., COPD).
* '''High (>29):''' [[Metabolic Alkalosis]] or compensation for chronic [[COPD]] (Respiratory acidosis).


===BUN and Creatinine===
===BUN and Creatinine===
* '''BUN (7–20 mg/dL)''' and '''Creatinine (0.6–1.2 mg/dL)'''
* Reflect renal clearance and glomerular filtration rate (GFR).
* '''[[Acute Kidney Injury]] (AKI):'''
* '''[[Acute Kidney Injury]] (AKI):'''
** Defined by acute rise in Creatinine.
** '''Prerenal:''' BUN:Cr ratio > 20:1. (Dehydration, poor perfusion).
** '''BUN:Cr Ratio > 20:1''' suggests prerenal etiology (dehydration) or upper GI bleed.<ref name="pmid32443130" />
** '''Intrinsic:''' BUN:Cr ratio < 15:1. (ATN, AIN, Glomerulonephritis).
** '''Postrenal:''' Obstruction (Stones, BPH).
* ''Pearl:'' Isolated elevated BUN (with normal Cr) is a sensitive indicator for [[Upper GI Bleed]] (digested hemoglobin).<ref name="pmid22396504">Srygley FD, Gerardo CJ, Tran T, Fisher DA. Does this patient have a severe upper gastrointestinal bleed? JAMA. 2012 Mar 14;307(10):1072-9. [https://pubmed.ncbi.nlm.nih.gov/22396504/ PubMed Abstract]</ref>


===Glucose===
===Glucose===
* '''Normal Range (Fasting):''' 70–100 mg/dL
* '''[[Hypoglycemia]] (<70):''' AMS, diaphoresis, seizure. Treat with D50/D10.
* '''Abnormalities:'''
* '''[[Hyperglycemia]]:'''
** [[Hypoglycemia]]: Critical when <70 mg/dL with symptoms.
** >250 with AG Metabolic Acidosis + Ketones = [[Diabetic Ketoacidosis]] (DKA).<ref name="pmid2754687">Kitabchi AE, Umpierrez GE, Murphy MB, et al. Management of hyperglycemic crises in patients with diabetes. Diabetes Care. 2001 Jan;24(1):131-53. [https://pubmed.ncbi.nlm.nih.gov/11194218/ PubMed Abstract]</ref>
** [[Hyperglycemia]]: Assess for [[Diabetic Ketoacidosis]] (DKA) or [[Hyperosmolar Hyperglycemic State]] (HHS) in patients with diabetes.<ref name="pmid22237220" />
** >600 with high osmolarity + no acidosis = [[Hyperosmolar hyperglycemic state]].
 
==Calculations==


===Calcium (Total)===
===Anion Gap (AG)===
* '''Normal Range:''' 8.5–10.2 mg/dL
* Used to differentiate causes of Metabolic Acidosis.<ref name="pmid17699401">Kraut JA, Madias NE. Serum anion gap: its uses and limitations in clinical medicine. Clin J Am Soc Nephrol. 2007 Jan;2(1):162-74. [https://pubmed.ncbi.nlm.nih.gov/17699401/ PubMed Abstract]</ref>
* Inclusion of calcium in routine panels (creating the Chem-8) aids in detecting hyperparathyroidism or malignancy, though it may lead to increased downstream testing without changes in diagnosis prevalence.<ref name="pmid33141903">Katzman BM et al. Is It Time to Remove Total Calcium from the Basic and Comprehensive Metabolic Panels? Clin Chem. 2020 Nov 1;66(11):1444-1449. [https://pubmed.ncbi.nlm.nih.gov/33141903/ PubMed Abstract]</ref>
* Formula: <math>AG = Na - (Cl + HCO3)</math>
* Correct for low albumin or check ionized calcium if status is unclear.
* '''Normal:''' 8–12 (varies by assay; >12 usually abnormal).
* '''High Gap Causes (MUDPILES):''' Methanol, Uremia, DKA, Paraldehyde, Iron/INH, Lactic Acidosis, Ethylene Glycol, Salicylates.
* ''Note:'' [[Hypoalbuminemia]] lowers the baseline AG. Corrected AG = Observed AG + 2.5 * (4 - Albumin).


==Calculations==
===Corrected Sodium (Hyperglycemia)===
* Formula: {Corrected Na} = {Measured Na} + 0.016 {Glucose} - 100)<ref name="pmid10225241" />
 
===Calcium Correction===
* If albumin is low, total calcium appears falsely low.
* Formula: {Corrected Ca} = {Measured Ca} + 0.8  (4 - {Albumin})<ref name="pmid4758544">Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. Br Med J. 1973 Dec 15;4(5893):643-6. [https://pubmed.ncbi.nlm.nih.gov/4758544/ PubMed Abstract]</ref>
* Or check an '''Ionized Calcium''' (iCa).


===Anion Gap===
==See Also==
Used to evaluate metabolic acidosis.
* [[Comprehensive Metabolic Panel]]
* Formula: <math>\text{AG} = \text{Na} - (\text{Cl} + \text{HCO}_3)</math>
* [[Anion Gap]]
* Normal: 8–12 mEq/L.
* [[Acute Kidney Injury]]
* High AG is associated with MUDPILES etiologies (e.g., DKA, uremia, toxic alcohols).<ref name="pmid22237220" />
* [[Hyperkalemia]] / [[Hypokalemia]]
* [[Hypernatremia]] / [[Hyponatremia]]


==References==
==References==
<references/>
{{reflist|2}}
 


[[Category:Emergency Medicine]]
[[Category:Critical Care]]
[[Category:Critical Care]]
[[Category:Nephrology]]
[[Category:Renal]]

Latest revision as of 00:29, 28 January 2026

Background

The Basic Metabolic Panel (BMP), often referred to as a Chem-7 or SMA-7, is one of the most frequently ordered laboratory tests in the Emergency Department. It provides a rapid assessment of fluid status, electrolytes, renal function, and glucose levels.[1]

Including Calcium technically makes the panel a Chem-8. It differs from the Comprehensive Metabolic Panel (CMP) by the lack of Liver Function Tests (LFTs).

Components and Reference Ranges

Reference ranges vary by laboratory. Typical adult values are listed below.[2]

Component Abbreviation Normal Range (US) SI Units
Sodium Na 135 – 145 mEq/L 135 – 145 mmol/L
Potassium K 3.5 – 5.0 mEq/L 3.5 – 5.0 mmol/L
Chloride Cl 95 – 105 mEq/L 95 – 105 mmol/L
Bicarbonate (Total CO2) HCO3 / CO2 22 – 29 mEq/L 22 – 29 mmol/L
Blood Urea Nitrogen BUN 7 – 20 mg/dL 2.5 – 7.1 mmol/L
Creatinine Cr 0.6 – 1.2 mg/dL 53 – 106 µmol/L
Glucose Glu 70 – 100 mg/dL (fasting) 3.9 – 5.6 mmol/L
Calcium Ca 8.5 – 10.2 mg/dL 2.1 – 2.6 mmol/L

Interpretation

Sodium (Na)

  • Hyponatremia (<135):
    • <120 mEq/L is a critical value (Risk of Seizure, coma).[3]
    • Assess volume status (Hypovolemic, Euvolemic, Hypervolemic).
    • Pearls: rule out Pseudohyponatremia (Hyperlipidemia/Hyperproteinemia) and Hyperglycemic induced (Corrected Na = Measured Na + 1.6 * [(Glucose - 100) / 100]).[4]
  • Hypernatremia (>145):
    • Almost always implies free water deficit (Dehydration).
    • Calculate Free Water Deficit.

Potassium (K)

Chloride (Cl)

  • Generally follows Sodium status.
  • Hyperchloremia: Often iatrogenic from large volume Normal saline resuscitation (Non-gap metabolic acidosis).
  • Hypochloremia: Gastric outlet obstruction/vomiting (Metabolic alkalosis).[2]

Bicarbonate (CO2)

  • Represents total venous CO2 content (mostly HCO3).
  • Low (<22): Metabolic Acidosis (most common in ED) or compensation for respiratory alkalosis.
  • High (>29): Metabolic Alkalosis or compensation for chronic COPD (Respiratory acidosis).

BUN and Creatinine

  • Acute Kidney Injury (AKI):
    • Prerenal: BUN:Cr ratio > 20:1. (Dehydration, poor perfusion).
    • Intrinsic: BUN:Cr ratio < 15:1. (ATN, AIN, Glomerulonephritis).
    • Postrenal: Obstruction (Stones, BPH).
  • Pearl: Isolated elevated BUN (with normal Cr) is a sensitive indicator for Upper GI Bleed (digested hemoglobin).[6]

Glucose

Calculations

Anion Gap (AG)

  • Used to differentiate causes of Metabolic Acidosis.[8]
  • Formula: <math>AG = Na - (Cl + HCO3)</math>
  • Normal: 8–12 (varies by assay; >12 usually abnormal).
  • High Gap Causes (MUDPILES): Methanol, Uremia, DKA, Paraldehyde, Iron/INH, Lactic Acidosis, Ethylene Glycol, Salicylates.
  • Note: Hypoalbuminemia lowers the baseline AG. Corrected AG = Observed AG + 2.5 * (4 - Albumin).

Corrected Sodium (Hyperglycemia)

  • Formula: {Corrected Na} = {Measured Na} + 0.016 {Glucose} - 100)[4]

Calcium Correction

  • If albumin is low, total calcium appears falsely low.
  • Formula: {Corrected Ca} = {Measured Ca} + 0.8 (4 - {Albumin})[9]
  • Or check an Ionized Calcium (iCa).

See Also

References

  1. ↑ Bertschi LA. Abnormal Basic Metabolic Panel Findings: Implications for Nursing. Am J Nurs. 2020 Jun;120(6):48-55. PubMed Abstract
  2. ↑ 2.0 2.1 Berend K, de Vries AP, GansRO. Physiological approach to assessment of acid-base disturbances. N Engl J Med. 2014 Oct 9;371(15):1434-45. PubMed Abstract
  3. ↑ Adrogué HJ, Madias NE. Hyponatremia. N Engl J Med. 2000 May 25;342(21):1581-9. PubMed Abstract
  4. ↑ 4.0 4.1 Hillier TA, Abbott RD, Barrett EJ. Hyponatremia: evaluating the correction factor for hyperglycemia. Am J Med. 1999 Apr;106(4):399-403. PubMed Abstract
  5. ↑ Montague BT, Ouellette JR, Buller GK. Retrospective review of the frequency of ECG changes in hyperkalemia. Clin J Am Soc Nephrol. 2008 Mar;3(2):324-30. PubMed Abstract
  6. ↑ Srygley FD, Gerardo CJ, Tran T, Fisher DA. Does this patient have a severe upper gastrointestinal bleed? JAMA. 2012 Mar 14;307(10):1072-9. PubMed Abstract
  7. ↑ Kitabchi AE, Umpierrez GE, Murphy MB, et al. Management of hyperglycemic crises in patients with diabetes. Diabetes Care. 2001 Jan;24(1):131-53. PubMed Abstract
  8. ↑ Kraut JA, Madias NE. Serum anion gap: its uses and limitations in clinical medicine. Clin J Am Soc Nephrol. 2007 Jan;2(1):162-74. PubMed Abstract
  9. ↑ Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. Br Med J. 1973 Dec 15;4(5893):643-6. PubMed Abstract
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