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Nursing Field Notes / Labs & Values · Panel page · Med-Surg + NCLEX
🧪 LABS & VALUES SET NG-194 Highest priority NG-042 BMP & electrolytes NG-121 CBC NG-153 WBC & coagulation NG-048 Renal labs 🧪 By condition 🩺 Bedside tests

BMP Panel & Electrolytes 🧪

Eight numbers from one tube — what each one tells you, and the patterns they make together

NG-042 LABS & VALUES · PANEL ADHD-friendly visual edition

The basic metabolic panel is the single most ordered blood test in the hospital, and it is the one you will be handed at 06:00 with a pen and no explanation. This page teaches it the way it is actually written — as a fishbone — then goes value by value, then teaches the two patterns that carry most of the exam questions: what the BUN : creatinine ratio means, and what CO₂ tells you about acid–base.

📄 Simple Nursing original — opens in Drive →

🧪 The 8Na · K · Cl · CO₂ · BUN · creatinine · glucose · calcium. Six in the fishbone, glucose on the point, calcium alongside.
💓 K⁺ is the priority3.5–5.0 mEq/L. Peaked T = high. Flat T + U = low. Never IV push.
🫘 BUN : CrOver 20:1 = DRY (pre-renal). About 10–15:1 with both raised = the kidney is hurt.
🧠 The four jobsSodium swells · Potassium pumps · Calcium contracts · Magnesium mellows.
⚠️ Read this before you memorize a single number. Every value on this page is a typical adult reference range — ranges vary by laboratory, so always use the range printed on your patient’s result. Critical-value cut-offs vary even more: every facility publishes its own critical list and its own call-back policy. Learn the direction and the meaning; verify the exact digits locally.
🧪

PART 1 · THE EIGHT VALUES

WHAT IS IN THE PANEL

One tube, eight numbers, and a shorthand you will see on every whiteboard.

FIGURE 1 · THE BMP “FISHBONE” — how the panel is actually written on a whiteboardTHE STANDARD SHORTHAND every unit uses · read it like a map: sodium always sits top-left, glucose always sits on the pointone tube ➡ eight numbersBMP = “chem 7” + calciumGREEN TOPlithium heparinplasma chemistryGOLD / SSTclot activator + gelserum chemistryEITHER of these tubesdepending on your laboratoryNa⁺ SODIUM135–145mEq/Lswells the body with fluidCl⁻ CHLORIDE97–107mEq/Lcopies sodium · acid–baseBUN10–20mg/dLprotein wasteK⁺ POTASSIUM3.5–5.0mEq/LPUMPS the heart · PRIORITYCO₂ / HCO₃⁻22–26mEq/Lthe BASE · acid–baseCREATININE0.6–1.2mg/dLkidney functionGLUCOSE70–110mg/dL (fasting)the brain’s fuelCa²⁺ CALCIUM9.0–10.5 mg/dLthe 8th BMP value — reported withthe panel, but not drawn inside thefishbone shorthandCELL COLOR = WHICH SYSTEM THAT VALUE REPORTS ONfluid / volumethe heartacid–base balancekidneyfuel + muscle📖 HOW TO READ A FISHBONE OUT LOUD• Top row, left to right: SODIUM · CHLORIDE · BUN. Bottom row, left to right: POTASSIUM · CO₂ · CREATININE.• The point on the right is always GLUCOSE. Calcium is reported with the panel but is not drawn in the fishbone.• A “BMP” is those eight. A “CMP” (comprehensive) adds liver values: albumin, total protein, bilirubin, ALT, AST, ALP.• These are typical adult reference ranges — ranges vary by laboratory, so read the range printed beside the result.

Figure 1 — the fishbone shorthand. Learn the positions, not just the numbers: on a real ward you will be shown this scribble long before you see a printed report.

🧪 The eight values, with their typical adult ranges

Sodium Na⁺135–145 mEq/Lswells the body with fluid
Potassium K⁺3.5–5.0 mEq/Lpumps the heart · PRIORITY
Chloride Cl⁻97–107 mEq/Lcopies sodium · acid–base
CO₂ / HCO₃⁻22–26 mEq/Lthe base · buffers the blood
BUN10–20 mg/dLprotein waste
Creatinine0.6–1.2 mg/dLkidney function
Glucose (fasting)70–110 mg/dLthe brain’s fuel
Calcium Ca²⁺9.0–10.5 mg/dLbones · clotting · beats

Typical adult reference ranges — ranges vary by laboratory, so always use the range printed on your patient’s result.

🧠 “Never Kick Cats Cruelly, Buy Cats Great Catnip.” Na · K · Cl · CO₂ · BUN · Creatinine · Glucose · Calcium — the eight, in fishbone order.

⭐ BMP vs CMP — what the extra letters buy you

BMP (basic) — 8 valuesCMP (comprehensive) — 14 values
Na · K · Cl · CO₂
BUN · creatinine · glucose · calcium		Everything in the BMP plus the liver:
albumin 3.5–5.0 g/dL · total protein · total bilirubin · ALT · AST · ALP

Order a BMP for fluid, electrolyte and kidney questions. Order a CMP when the liver, nutrition or a hepatotoxic drug is part of the picture.

🧠 Basic = body water and kidneys. Comprehensive = complete, liver included.

⏱️ When is the BMP drawn — and does it need fasting?

  • Routine daily labs are usually drawn in the early morning so the provider has them on rounds.
  • Glucose is the value affected by food. A fasting glucose needs roughly 8 hours with nothing but water; a random glucose is still useful, just interpreted differently.
  • After any change — a new diuretic, new IV fluids, dialysis, a blood transfusion, vomiting or diarrhea — expect a repeat panel.

Know why it was ordered. “Daily BMP” on a client started on furosemide is really a potassium watch.

🧠 Ask yourself: which single value is this panel really being drawn for? There is almost always one.
FIGURE 8 · ALL EIGHT BMP VALUES ON ONE AXIS EACHEIGHT TRAFFIC-LIGHT SCALES · low LEFT, high RIGHT · the sign sits under the end that causes ittypical adult reference rangesalways use your own lab’s rangeCRITICALLOWNORMAL 135–145HIGHCRITICAL120135145160mEq/LSODIUM Na⁺swells the body with fluid⬅ brain SWELLS: headache,confusion, seizures, comabrain SHRIVELS: thirst, dry ➡sticky tongue, flushed, agitatedCRITICALLOWNORMAL 3.5–5.0HIGHCRITICAL2.53.55.06.5mEq/LPOTASSIUM K⁺pumps the heart — PRIORITY⬅ flat T + U wave · shallowbreathing · weak · ileuspeaked T → wide QRS → ➡V-fib · tingling then weaknessLOWNORMAL 97–107HIGH97107mEq/LCHLORIDE Cl⁻copies sodium · acid–base⬅ vomiting, NG suction,loop diuretics → alkalosisdehydration, lots of ➡normal saline → acidosisLOWNORMAL 22–26HIGH2226mEq/LCO₂ / BICARBONATE HCO₃⁻the BASE — buffers the blood⬅ metabolic ACIDOSIS: DKA,renal failure, severe diarrheametabolic ALKALOSIS: ➡vomiting, NG suction, antacidsLOWNORMAL 10–20HIGHVERY HIGH102040mg/dLBUNprotein waste — easily fooled⬅ overhydration, liver failure,very low protein intakedehydration first, then ➡kidney disease · GI bleed · steroidsLOWNORMAL 0.6–1.2HIGHCRITICAL0.61.34.0mg/dLCREATININEthe kidney’s own handwriting⬅ low muscle mass(older adults, amputees)over 1.3 = a hurt kidney · ➡RISING day on day = acute injuryDEADLYLOWNORMAL 70–110HIGHCRITICAL5070110250mg/dLGLUCOSEthe brain’s only fuel⬅ shaky, sweaty, confused →seizure and coma. Treat FIRST.thirsty, polyuria, blurred ➡vision · ketones · DKACRITICALLOWNORMAL 9.0–10.5HIGHCRITICAL7.09.010.513mg/dLCALCIUM Ca²⁺bones · bloodletting (clotting) · beats⬅ TWITCHY: Trousseau, Chvostek,tetany, laryngospasm, long QTFLOPPY: stones, bones, ➡groans, moans, short QT

Figure 8 — all eight values on their own axis. This is the figure to photograph. Cover the writing and see whether you can say what happens at each end.

🩸

PART 2 · THE TUBE AND THE DRAW

BEFORE THE NUMBER EXISTS

Half of “abnormal” results are collection problems. Learn what breaks a sample.

FIGURE 2 · THE TUBE RACK — which color top gives you which panelSIX TUBES IN A RACK, drawn LEFT → RIGHT IN THE ORDER OF DRAW · the colored cap tells you the additive insidewrong tube = wrong resultor a repeat stick for the patient1LIGHT BLUEsodium citrateCOAGULATIONPT/INR · aPTT2GOLD / SSTclot activator + gelSERUM CHEMISTRYBMP · CMP · troponin3GREENlithium heparinPLASMA CHEMISTRYBMP · ammonia4LAVENDEREDTACBCH&H · WBC · platelets5GRAYfluoride oxalateGLUCOSE / LACTATEstops cells eating sugar6PINKEDTABLOOD BANKtype & screen · crossmatchORDER OF DRAW ➡🚨 WHY THE ORDER AND THE COLOR MATTER• Additives carry over between tubes. Filling them out of order lets one additive contaminate the next sample.• EDTA (lavender) carry-over into a chemistry tube falsely LOWERS calcium and falsely RAISES potassium.• An under-filled or over-shaken tube hemolyses — and hemolysis falsely RAISES potassium. That is the single most common “fake” critical value.• Never draw a chemistry sample above a running IV — draw from the opposite arm, or the result reflects the bag, not the patient.Tube colors and additives follow common practice — always confirm against your own facility’s specimen chart.

Figure 2 — the tube rack in order of draw. The cap color is not decoration: it tells you which additive is inside, and the additive decides which test the tube can be used for.

🩸 Which tube for which panel

CapAdditiveWhat it is for
Light blueSodium citrateCoagulation — PT/INR, aPTT. Must be filled to the line.
Gold / SSTClot activator + gelSerum chemistry — BMP, CMP, troponin, lipids
GreenLithium heparinPlasma chemistry — BMP, ammonia
LavenderEDTACBC — H&H, WBC, platelets, HbA1c
GrayFluoride oxalateGlucose / lactate — stops the cells consuming the sugar in the tube
PinkEDTABlood bank — type & screen, crossmatch

Colors follow common practice — confirm against your own facility’s specimen chart.

🧠 The blue coag tube must be filled to the line — the citrate-to-blood ratio is fixed. An under-filled blue tube gives a falsely prolonged PT/aPTT.

🚨 Hemolysis — the fake critical potassium

Answer first: a hemolysed sample falsely RAISES potassium. Red cells are packed with potassium; burst them and it spills into the serum.

Causes: a traumatic or slow draw, too small a needle, squeezing a fingerstick, shaking the tube instead of gently inverting it, an under-filled tube.

Never ignore a critical potassium just because you suspect hemolysis. Report it AND redraw per policy — both.

🧠 Hemolysis also falsely raises phosphate and magnesium and falsely lowers sodium. Anything stored inside the cell goes up when the cell breaks.

⚠️ Three more ways to ruin a good specimen

  • Drawing above a running IV. The sample is diluted by whatever is in the bag — draw from the opposite arm, or below the site with the infusion paused per policy.
  • Leaving the tourniquet on too long. Prolonged stasis concentrates the sample and raises potassium and calcium. Release it within about a minute.
  • Filling out of order. Additive carry-over — EDTA into a chemistry tube falsely lowers calcium and raises potassium.
🧠 Right arm, right tube, right order, right fill. Four rights, and the number you get is the number the patient actually has.
⚡

PART 3 · THE ELECTROLYTES

FOUR JOBS, FOUR IONS

Sodium swells, potassium pumps, chloride copies, calcium contracts — and magnesium mellows from just off-panel.

FIGURE 3 · WHY SODIUM IS REALLY A WATER LABTHREE CELLS, magnified ×2000 · read LEFT → RIGHT · in every panel the OUTSIDE fluid is what changed — the cell only reactswater always moves TOWARDthe saltier side1LOW SODIUM outsidehyponatremia · Na⁺ under 135NaNaNaNaNaNaNaNa💧 water moves IN → the cell SWELLS2NORMAL SODIUM outsideNa⁺ 135–145 mEq/LNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNa⚖️ water stays put → the cell holds its shape3HIGH SODIUM outsidehypernatremia · Na⁺ over 145NaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNaNa🏜️ water is pulled OUT → the cell SHRIVELSWHAT EVERY MARK MEANSsodium ion in the fluid OUTSIDE the cellwater movementthe cell (cytoplasm + nucleus)phospholipid bilayer — the cell membrane🧠 “Where sodium goes, water follows.”That is why sodium changes brain size, blood pressure and blood volume — and why it behaves like a NEURO lab, not a kidney lab.

Figure 3 — sodium changes cell size because water follows it. Everything sodium does to a patient follows from this one picture.

🧂 SODIUM — “sodium swells the body with fluid”

Range: 135–145 mEq/L. It is the main cation OUTSIDE the cell, and it drags water with it — so it sets blood volume and blood pressure.

LOW — hyponatremia“Low and slow.” Headache, confusion, mental status change, seizures, coma. Causes: excess water, SIADH, vomiting and diarrhea, diuretics, heavy sweating.
HIGH — hypernatremia“Big and bloated, dry inside.” Extreme thirst, dry sticky tongue, flushed skin, increased muscle tone, agitation. Causes: water loss, no access to water, diabetes insipidus, DKA, too much salt.
🧠 “Salt low = brain swells. Salt high = brain shrivels.” Sodium questions are neuro questions.
GO DEEPERCorrection speed and the seizure risk are on NG-194 · Highest priority.

💓 POTASSIUM — “potassium pumps the heart”

Potassium is the priority electrolyte — either direction can stop the heart. Range: 3.5–5.0 mEq/L. The main cation INSIDE the cell. Small changes make big rhythm problems, which is why it is the priority electrolyte.

HIGH — hyperkalemiaTall peaked T waves, then a widening QRS. Tingling then weakness. Hyperactive bowel sounds. Causes: renal failure, K-sparing diuretics, ACE inhibitors/ARBs, acidosis, crush injury and burns.
LOW — hypokalemiaFlat T wave, ST depression, U wave. Shallow respirations, weak legs, constipation and ileus. Causes: loop and thiazide diuretics, vomiting, diarrhea, NG suction, insulin, alkalosis.
🧠 “High and PEAKED, low and FLAT with a U.” One sentence covers both strips.
FIGURE 4 · HYPERKALEMIA — the four treatmentsONE HEART MUSCLE CELL in the center · the four numbered routes fan out in the order they are usually given · PROTECT → SHIFT → REMOVEnothing here is “the antidote”they do four different jobsnucleusCARDIAC MUSCLE CELLthe cell whose rhythm the potassium is wreckingKKKKKKKKKKTOO MUCH K⁺ in the blood around the cell1IV CALCIUM GLUCONATEPROTECT the membraneIt does NOT lower the potassium.It stabilizes the heart cell so thepotassium cannot trigger a lethal rhythm.Given first when the ECG is changing.2IV REGULAR INSULIN + 50% DEXTROSESHIFT it into the cellsInsulin drags potassium INTO the cell.The dextrose is there to stop theclient going hypoglycemic.Fast — but temporary. It hides, not fixes.3SODIUM POLYSTYRENE SULFONATEREMOVE it through the gutBinds potassium in the bowel so itleaves in the stool. Slow.Expect diarrhea — that is how it works.4HEMODIALYSISREMOVE it definitivelyThe answer when the kidneys are thereason the potassium is high, or whenthe level is extreme and the QRS is wide.ROUTE COLOR = WHAT THE TREATMENT DOESpotassium ion (K⁺)protectshift inwardremove via gutremove via dialysis🚨 AND BEFORE ANY OF ITCardiac monitor. Hold every potassium source — IV fluids with K⁺,supplements, salt substitutes, K-sparing diuretics, ACE inhibitors/ARBs.

Figure 4 — the four hyperkalemia treatments and where each one sends the potassium. Notice that only two of the four actually remove any.

✅ Replacing potassium safely — the rules

  • Never IV push. Always diluted, always on a pump.
  • Commonly a maximum of 10–20 mEq per hour peripherally, with a rhythm monitored.
  • Check urine output first — you cannot excrete what you cannot pass.
  • Burning at the site: slow the rate and check the site; tell the provider.
  • Oral potassium goes with food and a full glass of water.
  • If the potassium will not come up, check the magnesium.
🧠 “Fix the mag, then the K will lag no more.” Refractory hypokalemia is usually a magnesium problem wearing a potassium costume.

🧪 CHLORIDE — “chloride copies sodium”

Range: 97–107 mEq/L. It follows sodium almost everywhere, so a low sodium usually comes with a low chloride.

Where they differ is acid–base: high chloride pushes toward metabolic acidosis (lots of normal saline, dehydration) and low chloride toward metabolic alkalosis (vomiting, NG suction, loop diuretics).

🧠 Chloride is the electrolyte nobody revises and every so often the exam asks about. Cl⁻ copies Na⁺; the exception is acid–base.

🦴 CALCIUM — “calcium contracts the muscles”

Range: 9.0–10.5 mg/dL. The three B’s: Bones, Bloodletting (clotting) and Beats.

Albumin matters. About half the calcium in blood travels bound to albumin, so a client with a low albumin (normal 3.5–5.0 g/dL) can show a low total calcium while the active ionized calcium is fine. Check the albumin before you panic.

🧠 Low albumin fakes a low calcium. It is the single most common reason a calcium looks worse than the patient.
FIGURE 7 · THE TWO NAMED SIGNS OF LOW CALCIUMLEFT: Trousseau’s sign — an arm with a BP cuff inflated · RIGHT: Chvostek’s sign — a face tapped over the facial nervelow calcium = TWITCHYhigh calcium = FLOPPY1TROUSSEAU’S SIGNinflate a BP cuff above systolic for 1–3 minutesmmHgcuff inflated ABOVE systolicfingers held straightwrist and knuckles FLEXEDthumb pulled in✋ carpal spasm = POSITIVE = LOW CALCIUM🧠 “Trousseau = Tourniquet.” Twerking arm when the BP cuff goes on.2CHVOSTEK’S SIGNtap or stroke the cheek just in front of the earFACIAL NERVE (CN VII)the cheek and lip TWITCH😬 facial twitch = POSITIVE = LOW CALCIUM🧠 “Chvostek = Cheek.” Cheeky smile when you stroke the face.🧪 CALCIUM 9.0–10.5 mg/dL — and what each direction looks likeLOW Ca²⁺ — TWITCHYTrousseau’s · Chvostek’s · tetany · tingling round the mouth · prolonged QT · LARYNGOSPASM (the airway emergency) · diarrheaHIGH Ca²⁺ — FLOPPY“stones, bones, groans and moans” — kidney stones · bone pain · constipation · lethargy and weakness · shortened QTBOTH DIRECTIONSCheck the magnesium and the phosphate too — low magnesium and high phosphate both drag calcium down.

Figure 7 — the two named signs. Both are LOW calcium, and both also appear when magnesium is low or phosphate is high, because those drag calcium down.

🧘 MAGNESIUM — “magnesium mellows” (not in the BMP, but always nearby)

Range: 1.3–2.1 mEq/L — note the unit. Magnesium is reported in mEq/L on this site; some laboratories report it in mg/dL instead, so read the unit before you compare numbers.

LOW Mg²⁺The mellow is gone: hyperreflexia, tremor, seizures, and the top-tested rhythm — torsades de pointes and V-fib. Causes: malnourishment, chronic alcohol use, GI losses, diuretics.
HIGH Mg²⁺Super-mellow: absent deep tendon reflexes, depressed respirations, hypotension, bradycardia, heart block. Causes: renal failure, Mg-containing antacids and laxatives, IV magnesium.

Magnesium is ordered separately or as part of an extended panel — it is not one of the eight BMP values.

🧠 Check the DTRs. A disappearing reflex is the earliest warning that magnesium is climbing too high — before the breathing slows.
GO DEEPERAll six electrolytes side by side on NG-003 · All electrolytes cheat sheet (Renal + Fluid set) — the ranges on this page match it exactly.
🫘

PART 4 · BUN : CREATININE

THE KIDNEY HALF

Two numbers that only mean something as a pair.

FIGURE 5 · BUN : CREATININE — the ratio that says WHERE the problem isLEFT: a kidney in coronal section · RIGHT: the ratio drawn as a balance beam · read LEFT → RIGHTBUN is easily fooledcreatinine is notrenal artery — blood INrenal vein — blood OUTureter — urine OUTCORTEX — the filters (glomeruli) live hereMEDULLA — pyramids concentrate the urinerenal pelvis — urine collectsRIGHT KIDNEY · CORONAL SECTIONWHERE EACH MARKER COMES FROMand why one of them is far more honest than the otherBUN 10–20 mg/dLProtein waste. The liver turns ammonia into urea; the kidney excretes it.Rises with dehydration, a high-protein diet, GI bleeding and steroids —even when the kidneys are perfectly healthy.CREATININE 0.6–1.2 mg/dLMuscle waste, produced at a steady rate by ordinary wear and tear.Filtered and barely reabsorbed, so it tracks kidney function almost purely.Over 1.3 = a hurt kidney. Rising day on day = an injury happening now.1PRE-RENAL — “dry”the kidney is fine; the delivery is notBUN ⬆⬆Creat →ratio OVER 20 : 1Dehydration · hemorrhage · shockheart failure · vomiting & diarrheaBUN climbs, creatinine barely moves2INTRA-RENAL — “damaged”the kidney tissue itself is injuredBUN ⬆Creat ⬆ratio about 10–15 : 1Acute tubular necrosis · toxic drugsglomerulonephritis · long ischemiaBOTH of them climb together🧠 HOW TO USE THE RATIO IN ONE SENTENCE• High BUN + normal creatinine = the patient is DRY (pre-renal).• High BUN + high creatinine = the KIDNEY itself is hurt (intra-renal).• Then check the third possibility — POST-renal: an obstruction (stone, enlarged• prostate, tumor) backing urine up. Bladder scan and check the hourly output.

Figure 5 — where each marker comes from, and the ratio drawn as a balance. The tilt of the beam is the whole diagnosis.

🫘 BUN — the number that is easily fooled

Range: 10–20 mg/dL. Urea is protein waste: the liver turns ammonia into urea and the kidney excretes it.

Raised by things that are not the kidney: dehydration, a high-protein diet, GI bleeding (blood is protein), steroids, burns, and heart failure.

Lowered by: overhydration, liver failure (no urea is made), very low protein intake, pregnancy.

🧠 Think of a protein bar wrapper — urea is the packaging the body throws away after using the protein.

🧪 CREATININE — the kidney’s own handwriting

Range: 0.6–1.2 mg/dL. Muscle waste, produced at a steady rate by ordinary wear and tear, filtered and barely reabsorbed.

  • Over 1.3 = a hurt kidney.
  • Rising day on day = an injury happening right now.
  • Low muscle mass (older adults, amputees, prolonged bed rest) can hide kidney damage behind a “normal-looking” creatinine.

Pair it with urine output: under 30 mL/hr is kidney distress.

🧠 BUN can lie. Creatinine rarely does. When they disagree, believe the creatinine.
GO DEEPERFull detail, GFR staging and urinalysis on NG-048 · Renal labs.

🧩 The ratio, in three lines

> 20 : 1PRE-RENAL
The patient is DRY. BUN climbs, creatinine barely moves. Dehydration, hemorrhage, shock, heart failure, vomiting and diarrhea. Fix the volume and the numbers come back.
10–15 : 1INTRA-RENAL
The kidney tissue is injured. Both climb together. Acute tubular necrosis, nephrotoxic drugs, glomerulonephritis, prolonged ischemia.
CHECKPOST-RENAL
Something is blocking the exit. Stone, enlarged prostate, tumor, clamped or kinked catheter. Bladder scan and check the hourly output before you assume the kidney has failed.
🧠 Dry · Damaged · Dammed. Three D’s, three places the problem can be: before the kidney, in it, or after it.

🚨 The renal-failure pattern you can predict

When the kidney fails, the panel moves in a predictable direction:

  • ⬆ Potassium — cannot excrete it. This is the lethal one.
  • ⬆ BUN and creatinine — cannot clear the waste.
  • ⬆ Phosphate and ⬆ magnesium — cannot excrete them either.
  • ⬇ Calcium — pushed down by the high phosphate, and the failing kidney cannot activate vitamin D.
  • ⬇ CO₂ / bicarbonate — acid builds up, so metabolic acidosis develops.

Never give a potassium-containing IV or a potassium-sparing diuretic in renal failure without a deliberate order and a current level.

🧠 “Kidneys quit → K, Phos and Mag climb; Calcium and bicarb fall.” Learn the shape and you can predict half a panel.
🧩

PART 5 · THE PATTERNS

READ IT AS A SHAPE

Individual values are facts. Patterns are diagnoses.

FIGURE 6 · CO₂ AND BICARBONATE — the two halves of the pH seesawSIDE VIEW OF A BALANCE · the LUNGS control the acid on the left, the KIDNEYS control the base on the right · the pH is the pointerCO₂ = carbon di-ACIDHCO₃ = BI-CARB is BASEACID sideCO₂ · H⁺BASE sideHCO₃⁻LUNGSblow CO₂ OFF → less acidhold CO₂ IN → more acidKIDNEYSkeep HCO₃ → more basedump HCO₃ → less baseACIDOSISNORMALALKALOSIS7.357.45pH — the pointer on the seesaw📖 READING THE SEESAW — ROME: Respiratory Opposite, Metabolic EqualpH ⬇ + CO₂ ⬆RESPIRATORY ACIDOSIShypoventilation · COPD · opioids · a tiring patientpH ⬆ + CO₂ ⬇RESPIRATORY ALKALOSIShyperventilation · anxiety · pain · early sepsispH ⬇ + HCO₃ ⬇METABOLIC ACIDOSISDKA · renal failure · severe diarrhea · shockpH ⬆ + HCO₃ ⬆METABOLIC ALKALOSISvomiting · NG suction · too many antacids

Figure 6 — the CO₂ on a BMP is the bicarbonate (the base). It is the metabolic half of the acid–base picture, and it moves the same way as the pH.

🧪 The CO₂ on a BMP is NOT the CO₂ on an ABG

The CO₂ on a BMP is the bicarbonate, not the arterial gas.

BMP “CO₂” = total CO₂ ≈ HCO₃⁻22–26 mEq/L — this is the BASE, controlled by the kidneys. A metabolic number, drawn from a vein.
ABG “PaCO₂”35–45 mmHg — this is the ACID, controlled by the lungs. A respiratory number, drawn from an artery.

Same two letters, opposite meanings. Read the units: mEq/L = the bicarbonate; mmHg = the arterial gas.

🧠 “Carbon di-ACID in the artery, bi-CARB is BASE in the vein.” Units tell you which one you are holding.

📈 ROME — reading acid–base in two seconds

Respiratory Opposite · Metabolic Equal.

PatternNameClassic causes
pH ⬇ · CO₂ ⬆Respiratory acidosisHypoventilation · COPD · opioids · a tiring patient
pH ⬆ · CO₂ ⬇Respiratory alkalosisHyperventilation · anxiety · pain · early sepsis
pH ⬇ · HCO₃ ⬇Metabolic acidosisDKA · renal failure · severe diarrhea · shock
pH ⬆ · HCO₃ ⬆Metabolic alkalosisVomiting · NG suction · excess antacids
🧠 ROME. If the pH and the CO₂ move in opposite directions it is the lungs; if the pH and the bicarbonate move together it is metabolic.

🍬 GLUCOSE on a BMP

Fasting 70–110 mg/dL (many laboratories use the tighter fasting 70–99).

  • Under 70 — treat. Under 50 is an emergency: the brain has no stored fuel.
  • Over 120 fasting — think uncontrolled diabetes, steroids, stress response, infection, TPN.
  • A stress hyperglycemia in an acutely unwell client is common and does not by itself mean diabetes.

Remember the interaction with potassium: insulin drives potassium into cells, so treating a high glucose can drop the potassium.

🧠 Insulin moves sugar AND potassium into the cell. That is why it appears in the hyperkalemia protocol.

🧩 Four whole-panel patterns worth recognizing on sight

PanelThink
Na ⬆ · BUN ⬆ · BUN:Cr > 20:1 · Hct ⬆Dehydration. Everything looks concentrated because the water left.
K ⬆ · BUN ⬆ · Cr ⬆ · CO₂ ⬇ · Ca ⬇Renal failure. The classic shape — waste up, base down, calcium down.
Glucose ⬆⬆ · K variable · CO₂ ⬇ · Na ⬇DKA. Metabolic acidosis with a dilutional low sodium; total-body potassium is depleted even when the serum level looks normal.
K ⬇ · Cl ⬇ · CO₂ ⬆Vomiting or NG suction. Losing acid and chloride → metabolic alkalosis.
🧠 Read a panel as a shape, not a list. Four shapes will carry you a long way.

✅ What you actually do with a BMP on shift

1Scan for the critical values first: potassium, sodium, glucose.
2Compare with yesterday. A trend beats a snapshot every time.
3Ask why it was ordered — new diuretic? new IV fluids? dialysis day?
4Look at the client: level of consciousness, respirations, reflexes, bowel sounds, urine output, daily weight.
5Hold or question any drug the result makes unsafe, and report with a recommendation.
🧠 Numbers, trend, reason, patient, action. Five steps, every panel, every shift.

🎯 Cover & check — 8 rapid-fire questions

Q1. Name the eight components of a BMP in fishbone order.
Show answerSodium · chloride · BUN on the top row; potassium · CO₂ · creatinine on the bottom row; glucose on the point; calcium reported alongside.
Q2. BUN 48, creatinine 1.1. What is the ratio telling you?
Show answerRoughly 44:1 — well over 20:1 with a normal creatinine. Pre-renal: the client is dry. Think dehydration, hemorrhage, heart failure.
Q3. Which tube does a BMP go in, and which tube must be filled exactly to the line?
Show answerBMP: gold/SST or green. The one that must be filled to the line is the light blue citrate coagulation tube.
Q4. A potassium comes back at 6.4 on a client who had a difficult, traumatic draw. What do you do?
Show answerReport it and redraw — both. Hemolysis can falsely raise potassium, but you never sit on a critical value while you wait.
Q5. What is the reference range for magnesium on this site, and in what unit?
Show answer1.3–2.1 mEq/L. Note the unit — some laboratories report magnesium in mg/dL instead.
Q6. The CO₂ on a BMP is 18. Which acid–base disturbance does that suggest?
Show answerA low bicarbonate → metabolic acidosis. Think DKA, renal failure, severe diarrhea, shock.
Q7. Total calcium is 7.8 and albumin is 2.4. Is the client necessarily hypocalcemic?
Show answerNot necessarily. About half of blood calcium is bound to albumin, so a low albumin lowers the total calcium while the ionized calcium may be normal. Correlate with the client and the ionized level.
Q8. Your client’s potassium will not come up despite replacement. What do you check?
Show answerThe magnesium. Low magnesium makes hypokalemia refractory.
🧪 The eightNa 135–145 · K 3.5–5.0 · Cl 97–107 · CO₂ 22–26 · BUN 10–20 · Cr 0.6–1.2 · glucose 70–110 · Ca 9.0–10.5. Typical adult ranges — check your lab.
💓 K⁺ firstPeaked T = HIGH · flat T + U = LOW. Never IV push. Protect (calcium) → shift (insulin + D50) → remove (binder, dialysis).
🫘 RatioOver 20:1 = DRY. 10–15:1 with both up = the kidney is hurt. Then rule out an obstruction.
🧠 Units matterBMP CO₂ = bicarbonate in mEq/L (base, kidneys). ABG PaCO₂ in mmHg (acid, lungs). Magnesium 1.3–2.1 mEq/L.