Labs to know for the NCLEX Nursing Exam


by Justine Buick, MSN, RN

I’m not sure if anyone loves learning their labs and understanding them, but I do! I think this is one aspect that separates the baby nursing students from the adult nursing students. If you don’t understand labs, forget it. But I’m here to help!

Labs to Know…

If you have different values memorized already, use that number as long as it’s close to what I have below. To memorize labs, use a blank sheet or make your own. Fill in the values and/or indications as many times as you need to until you have it memorized. I made a labs sheet! You can use mine.

labs sheet

It’s best to learn labs by systems:

1) Electrolytes
2) Hematology
3) Respiratory
4) Renal
5) Gastrointestinal
6) Pancreatic
7) Cardiac
8) Coagulation
9) Random labs
10) Vital signs
11) Newborn

These lab values do not indicate every possible disease that could be associated with it or everything that could be on the NCLEX- just the most common and important for taking the NCLEX. I have simplified it greatly so you can have a basic but necessary understanding. 

1) Electrolytes

Na/sodium: 135-145
critical values: <120 and >160
Indicates fluid balance.
Early symptoms are neuro changes, but can also affect muscles and respiratory muscles.
There is an inverse relationship with K. 

K/potassium: 3.5-5
critical values: <2.5 and >6.5
Abnormal values can cause arrhythmias.
There is an inverse relationship with Na.

Ca/calcium: 8.5-10.5
Affects muscles.
Increased Ca acts like a sedative.
There is an inverse relationship with phosphorous.

Mg/magnesium: 1.6-2.6
critical values: <0.5 and >3
Affects muscles.
Increased Mg acts like a sedative.
Calcium gluconate is antidote to too much Mg.

Phosphorus: 2.5-4.5
There is an inverse relationship with Ca.

2) Hematology

Many NCLEX questions involve questions regarding infection or bleeding.

WBC/white blood cell count: 5-10K
critical values: <2500 and >30,000
Increased indicates infection.
Decreased indicates immunosuppresion.


critical values: <5 and >20
Decreased indicates possible need for blood transfusion, active bleeding or anemia. You always want to see the trend (a major drop in one day would indicate active bleeding)


42-52 men
37-47 women
critical values: <15 and >60

Platelets: 150,000-400,000
critical values: <50,000 and >1 million
Decreased indicates increased risk for bleeding. You always want to see the trend (a major drop in one day would indicate bleeding).
– If value is low initiate bleeding precautions.
– Monitor platelets with chemotherapy patients b/c risk of thrombocytopenia.

RBC/red blood cell count: 4.5-6 million
Decreased indicates anemia.

3) Respiratory labs

ABGs/Arterial Blood Gases.  These labs are for Respiratory/Metabolic- Acidosis/Alkalosis.

Ph: 7.35-7.45

HCO3/bicarbonate: 22-26
Abnormal level indicates a renal issue.

PCO2/carbon dioxide: 35-45
Abnormal level indicates a respiratory issue.

PO2: 80-100

d-dimer:  positive indicates a bleeding problem like pulmonary embolism, dvt, stroke or DIC

Ventilation/Perfusion scan: Positive indicates pulmonary embolism

4) Renal labs

Many drugs are toxic to kidneys (and liver).

BUN/blood urea nitrogen: 5-25
Increased indicates poor kidney perfusion.

Creatinine: 0.6-1.35
Increased indicates poor kidney perfusion.

Urine output: at least 30 mL/hour

Urine specific gravity: 1.005-1.030
Elevated indicates dehydration.
Decreased indicates overhydrated.

5) GastroIntestinal labs

ALT: 4-36
Increased indicates hepatitis.
Many drugs are toxic to liver.

AST: 0-35
Increased indicates hepatitis.
Many drugs are toxic to liver.

bilirubin: total 0.3-1. indirect 0.2-0.8. direct 0.1-0.3.
Increased indicates hepatitis or cholecystitis.

total cholesterol:  < 200
Increased indicates risk factor for angina
Have client fast 12-24 hours after eating a low-fat meal before testing

LDL cholesterol (low density lipoprotein)
The “Bad” cholesterol: 
< 130

HDL cholesterol (high density lipoprotein)
The “Happy” cholesterol: 

>45 men
>55 women

ammonia: Increased indicates liver disease.

albumin” 3.5-5
Decreased indicates poor nutrition.

6) Pancreas Labs

Lipase: 10-140
Increased indicates pancreatitis.

Amylase: 25-130
Increased indicates pancreatitis.

A1C/glycosylated hemoglobin: >7% is considered elevated.
Indicates blood sugar control over last 2-3 months.

fasting blood sugar: 70-110
Can be increased when on steroids.

7) Cardiac Labs 

Just know that increased values are bad.

Troponins: Increased indicate Myocardial Infarction.
Onset after 1 hour.

CK or CPK: Increased indicate MI.
Onset in 4-6 hours.

CK-MB: Increased indicate MI.
Onset in 4-6 hours.

Myoglobin: Increased indicate MI.
Onset in 1-4 hours

BNP (B-type natriuretic peptide): Increased indicates diagnosis of CHF.

central venous pressure: 3-8
increased indicates too much fluid.

8) Coagulation

These labs are important to know so that you don’t let your client bleed to death or put them at risk for blood clots.

PTT: Therapeutic is 1.5x – 2.5x normal/control.
Used to regulate IV heparin, not subq heparin.
Antidote is protamine sulfate.
Used as to screen for coagulation disorders.

aPTT: Therapeutic is 1.5x – 2.5x normal/control.
Used to regulate IV heparin.
Antidote is protamine sulfate.

PT: Therapeutic is 1.5x – 2x normal/control.
Used to regulate warfarin.
Antidote is Vitamin K.

INR: 0.8-1.1 normal
Therapeutic is 2-3. Higher with heart valves or higher risk for clots. Do not let it get greater than 4.5.
Used to regulate warfarin.

9) Random labs/values

Uric acid: Increased indicates gout.

C-reactive protein: Used to detect very low-grade inflammatory responses.

ESR/erythrocyte sedimentation rate: 0-20
increased indicates an inflammatory process.

10) Vital Signs: Adult

Vital Signs: Adult
HR: 60-100
RR: 12-18
BP: 110-120 (systolic), 60-90 (diastolic)
Temperature: 96.8-100.4F, 36-38C.
O2 (oxygen saturation) 93-100%.

11) Vital Signs: Newborn

Vital signs: Newborn
RR: 30-60, uneven breaths is normal, count for 1 minute.
HR: 120-160, auscultate for 1 minute.
Temperature: 97.7-99.4F, 36.5C-37.5C, insert 1/4-1/2 inch rectally, avoid perforating rectum, hold legs to prevent trauma.
BP: 80/50, usually not measured.

bilirubin – newborn: 1-12
Avoid elevated levels in newborn, called hyperbilirubinemia.


Those are the labs! If think something needs to be added or if you have any questions, just post them in the comments.


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