Everything You Need To Know About Lab Values For The NCLEX

Learning about labs is intimidating and can be very difficult. There are a lot of numbers, unfamiliar terms and units of measurement. When it comes to studying lab values for the NCLEX it is important to know that they are not something you will be able to master in an hour. The best way to learn lab values for the NCLEX is to practice consistently and continue to review them over time.

Don’t beat yourself up about memorizing every single value but you should have a general idea of all the most important and common lab value ranges. You will notice that lab values may differ slightly depending on what book or resource you are using to study. The NCLEX will not give you a lab value that is only slightly out of range. In most cases the NCLEX will use lab values that are extremely abnormal so that you can recognize them.

Blood and urine tests are one of the most important methods a doctor will use to diagnose a patient. As nurses we need to know what the normal lab values are and what to do if they are abnormal. The NCLEX is about testing you to see if you are safe to practice as a new nurse. Patient safety is your top priority. In order to keep your patients safe you are expected to know normal lab ranges of the most common laboratory tests. Knowing your lab values will allow you to be safe while administering medications and working as a nurse.

These blood tests assess electrolytes, glucose, fluid, renal function, and liver function all with one test. This test is essential for patients with conditions such as electrolyte imbalances, diabetes, kidney issues, liver issues, and fluid imbalances.

You will have questions on your NCLEX relating to these numbers. Electrolyte values are extremely important to know because they can cause cardiac issues when they are not within range. You should know the normal fasting blood glucose range as it relates to diabetes. Knowing the general kidney and liver tests will be helpful as it can be an indication of organ failure or injury. You will need to memorize these ranges and know what you should be concerned about if they are abnormally high or low.

• Fasting Glucose: 70 - 100 mg/dL
• Potassium: 3.5 - 5 mEq/L
• Sodium: 135 - 145 mEq/L
• Magnesium: 1.5 - 2.5 mg/dL
• Calcium: 8.5 - 10.5 mg/L
• Chloride: 95 - 105 mEq/L
• Phosphorus: 2.5 - 4.5 mg/dL
• BUN: 5 - 20
• Creatinine: 0.6 - 1.2 mg/dL
• Albumin: 3.4 - 5.4 g/dL
• Bilirubin: 0.1 - 1 mg/dL
• ALP, ALT, and AST (know that these are enzymes found in the liver, if they are elevated it suggests that the patient is having liver issues)

The CBC is another blood test you will see often. This test indicates the amount of cells in the blood such as red blood cells, hemoglobin, hematocrit, platelets, and white blood cells. This test is especially important for people with conditions including anemia, infections, and clotting disorders. You should know these values and know what to be concerned about if they are abnormally high or low.

• Red Blood Cells: 4.5 - 5.5 Million
• White Blood Cells: 5,000 - 10,000
• Platelets: 150,000 - 400,000
• Hemoglobin:
  • 12 -16 g/dL for women
  • 14 - 18 g/dL for men
• Hematocrit:
  • 37% - 47% for women
  • 42% - 52% for men

This test is different from the others because it is taken from an artery instead of a vein. It is normally the first test a doctor orders when they suspect that the patient has a respiratory or metabolic disorder. It assesses the acid-base imbalances in the body. If a patient has a severe imbalance, medications, fluids, oxygen, and intubation may be ordered. You should have learned to interpret ABGs in nursing school. If needed, go back and review your books and notes on how to do this.

• pH: 7.35 - 7.45
• pCO2: 35 - 45 mmHg
• HCO3: 22 - 26 mEq/L
• pO2: 80 - 100%

These lab tests are critical for patients on anticoagulants or who have a bleeding disorder. Oftentimes these patients have to get these tests done on a regular basis and medications may have to be adjusted depending on the results. It is dangerous when these values are subtherapeutic or toxic and it can be lethal to the patient. You need to be able to recognize when these values are out of range and what you should do.

• PT (Prothrombin Time): 10 - 12
• INR (International Normalized Ratio):
  • If the patient is not on warain: <1
  • If the patient is on warain: 2 - 3
• aPTT (Activated Partial Thromboplastin Time):
  • If the patient is not on heparin: 30 - 40 seconds
  • If the patient is on heparin: 60 - 100 seconds

This is another extremely common blood test that you should be familiar with. It tests for cholesterol and triglycerides. If a patient’s cholesterol is too high, medication, diet, and exercise are normally prescribed.

• Total Cholesterol: < 200 mg/dL
• LDL: < 100 mg/dL
• HDL: > 60 mg/dL
• Triglycerides: < 150 mg/dL

Diabetes is a common disease and you need to be familiar with what an A1C indicates. This test indicates the average blood glucose level over the past three months. If a patient has poor blood glucose control, their A1C will be high and adjustments should be made to their lifestyle and medications.

• For Patients Without Diabetes: 4 - 6%
• For Patients With Diabetes: < 7%

You should know the common drug level ranges. Some medications have therapeutic ranges which need to be monitored. If the drug is subtherapeutic it means that there is not enough of it in the patient’s system and it will not be very effective. If a patient has too much of a drug in their system it could be toxic and life threatening.  This is critical for patients that are on the following medications.

• Digoxin: 0.5 - 2 ng/mL
• Lithium: 0.5 - 1.2 mmol/L
• Carbamazepine: 4 - 10 mcg/mL
• Dilantin: 10 -20 mcg/mL
• Theophylline: 10 - 20 mcg/mL
• Phenobarbital: 15 - 40 mcg/mL
• Valproic Acid: 50 - 100 mcg/mL

Learning lab values is extremely important to your success on the NCLEX and as a nurse. They are not something you can sit down and learn in one study session. You must take your time and review them consistently during your studies. Don’t get overwhelmed by all the numbers and units of measurement. Different references will have slightly different ranges. You need to know the normal ranges and be able to recognize when a value is grossly abnormal. It will take time to learn all of the lab values, what they mean, and how to apply it to patient care. Remember that patient safety is always your number one concern when it comes to lab values.