Memorizing Lab Values the Easy Way

064019Here you are again, burning midnight candles and studying for your exams. It’s another bloody night and you’re so tired of reading and memorizing lab values. However, you know that doing so is not only necessary to pass the exam, but when it comes to the clinical area also. Here are tricks on how to remember the values more easily.

Hemoglobin and Hematocrit (H and H)

  • General rule of thumb is a 1:3 ratio
  • Hematocrit should be approximately 3X the Hemoglobin
  • Norm ~ Hgb 10 / Hct 30 (minimum values)
  • Also Hgb 13 / Hct 40 accepted

BUN and Creatinine (Cr)

  • General rule of thumb is a 1:20 ratio
  • BUN should be approximately 20x the Creatinine
  • Norm ~ BUN 20 / Cr 1.0

Sodium (Na)

  • You may try memorizing the last two digits
  • The last two digits were the same for a normal pH level
  • (normal pH ~ 7.35 – 7.45)
  • Normal Na ~ 135-145

Potassium (K) and Magnesium (Mg)

  • These two electrolytes have a great influence over each other
  • Significant cardiac involvement
  • Memorize and use them together as a pair – always
  • K ~ 3.5-5.2 (You may try memorizing 5 as a limit)
  • Mg ~ 1.8-3.0 (Some try memorizing 2.5 as acceptable; 2.5 happens to be half of 5.0)

Phosphorus (Phos) and Calcium (Ca)

  • These two electrolytes have an inverse relationship. As one increases, the other decreases, and vice-versa
  • Phos sometimes gets treated as a trio with K and Mg (depends on the physician ordering or treating abnormal levels)
  • Normal Phos ~ 2.4-5.1
  • You could start by using 2.5 as minimum reference (since you already are memorizing that number for Mg)


Liane Clores, RN MAN

Currently an Intensive Care Unit nurse, pursuing a degree in Master of Arts in Nursing Major in Nursing Service Administration. Has been a contributor of Student Nurses Quarterly, Vox Populi, The Hillside Echo and the Voice of Nightingale publications. Other experience include: Medical-Surgical, Pediatric, Obstetric, Emergency and Recovery Room Nursing.

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