Commonly Used Abbreviations
General
| Abbreviation | Meaning | Abbreviation | Meaning |
|---|---|---|---|
| ā | Before | ½ NS | Half normal saline (0.45% NaCl) |
| c̄, w/ | With | p̄ | After |
| D₅NS | Dextrose 5% in normal saline | per | By or through |
| D₅W | Dextrose 5% in water | LR | Lactated Ringer's |
| gtt(s) | Drop, drops | Rx | Prescription |
| NPO | Nothing by mouth | s̄, w/o | Without |
| NS | Normal saline (0.9% NaCl) | Sig. | Directions (write on label) |
Route
| Abbreviation | Meaning | Abbreviation | Meaning |
|---|---|---|---|
| G-Tube | Gastrostomy tube | NG | Nasogastric tube |
| ID | Intradermal | NJ | Nasojejunal tube |
| IM | Intramuscular | OG | Orogastric tube |
| IV | Intravenous | PO | By mouth or orally |
| IVP | Intravenous push | PR | By rectum |
| IVPB | Intravenous piggyback | SL | Sublingual |
| J-Tube | Jejunal tube | SUBQ | Subcutaneous |
Frequency
| Abbreviation | Meaning | Abbreviation | Meaning |
|---|---|---|---|
| AC | Before meals | pm | Afternoon or evening |
| am | Before noon | prn, PRN | As needed |
| b.i.d., BID | Twice a day | q (e.g., q2h, q4h) | Every (e.g., every 2 hours, every 4 hours) |
| h, hr | Hour | q.i.d., QID | Four times a day |
| HS | Bedtime | STAT | Immediately |
| min | Minute | t.i.d., TID | Three times a day |
| PC | After meals |
Error-Prone Abbreviations
Do Not Use
The following abbreviations are on the official "Do Not Use" lists from the Institute for Safe Medication Practices (ISMP) and/or the Joint Commission. Although you may see these in clinical practice, they are not recommended.
Route / Location
| Abbreviation | Meaning |
|---|---|
| IJ | Injection |
| IN | Intranasal |
| SQ | Subcutaneous |
Frequency
| Abbreviation | Meaning |
|---|---|
| Q.D., q.d., q1d | Every day |
| qhs | Every night at bedtime |
| Q.O.D., q.o.d. | Every other day |
Other
| Abbreviation | Meaning | Abbreviation | Meaning |
|---|---|---|---|
| µg | Microgram | MS, MSO₄ | Morphine sulfate |
| cc | Cubic centimeters | U, IU | Units, international units |
| MgSO₄ | Magnesium sulfate |
Metric & Household Units of Measure
| Measurement Type | Metric System | Household System |
|---|---|---|
| Mass / Weight | microgram (mcg), milligram (mg), gram (g), kilogram (kg) | pound (lb), ounce (oz) |
| Volume | milliliter (mL), deciliter (dL), liter (L) | fluid ounce (fl oz), tablespoon (Tbsp), teaspoon (tsp) |
| Length | millimeter (mm), centimeter (cm), meter (m) | inch (in), foot (ft), yard (yd) |
| Time | second (sec), minute (min), hour (hr) | |
Metric System Prefixes
| Prefix | Meaning | Example |
|---|---|---|
| Micro- (µ) | One millionth | 1 gram = 1,000,000 micrograms 1/1,000,000 g = 1 µg (mcg)* |
| Milli- (m) | One thousandth |
1 gram = 1,000 milligrams · 1/1,000 g = 1 mg 1 liter = 1,000 milliliters · 1/1,000 L = 1 mL 1 meter = 1,000 millimeters · 1/1,000 m = 1 mm |
| Centi- (c) | One hundredth | 1 meter = 100 centimeters 1/100 m = 1 cm |
| Deci- (d) | One tenth | 1 liter = 10 deciliters 1/10 L = 1 dL |
| Kilo- (k) | One thousand | 1,000 grams = 1 kilogram 1/1,000 kg = 1 g |
* Use abbreviation "mcg" for medical documentation (not µg).
Conversions
Metric ↔ Household
1 kg=2.2 lbs
30 mL=1 fl oz
15 mL=1 Tbsp
5 mL=1 tsp
2.54 cm=1 inch
Household System
1 lb=16 oz
1 Tbsp=3 tsp
1 cup=8 fl oz
1 pint=2 cups
1 quart=2 pints
1 gallon=4 quarts
1 foot=12 inches
Temperature Conversions
Fahrenheit → Celsius
°C = (°F − 32) ÷ 1.8
Celsius → Fahrenheit
°F = (°C × 1.8) + 32
Military Time Conversions
Military Time → Standard Time
| Military Time | Instructions to Convert to Standard Time | |
|---|---|---|
| 0000 – 0059 | → | Add 12 hours (i.e., 1200), add colon and "am" |
| 0100 – 1159 | → | Add colon and "am"; drop the leading zero if applicable |
| 1200 – 1259 | → | Add colon and "pm" |
| 1300 – 2359 | → | Subtract 12 hours (i.e., 1200), add colon and "pm" |
Standard Time → Military Time
| Standard Time | Instructions to Convert to Military Time | |
|---|---|---|
| 12:00 am – 12:59 am | → | Subtract 12 hours, remove colon and "am". Include zeros so there are two digits for the hour and two digits for the minutes |
| 1:00 am – 11:59 am | → | Remove colon and "am". If the hour is a single digit, add a zero before it to ensure two digits for the hour and two digits for the minutes |
| 12:00 pm – 12:59 pm | → | Remove colon and "pm" |
| 1:00 pm – 11:59 pm | → | Add 12 hours, remove colon and "pm" |
Oral Medications
Oral meds come as tablets, capsules, or liquids (syrups/suspensions). The goal: figure out how many tablets or how many mL to give.
For simple, one-step problems use Desired over Have (D/H × Q). For anything with unit conversions, Dimensional Analysis (DA) is safer and always works.
Method 1 — Desired ÷ Have × Quantity
D/H × Q Formula
Desired ÷ Have × Quantity = Answer
Use this when everything is already in the same units — no conversions needed.
📖 Worked Example — Tablet
| Step | Action |
|---|---|
| Order | Metformin 1000 mg PO · On hand: 500 mg tablets |
| Identify | D = 1000 mg · H = 500 mg · Q = 1 tablet |
| Calculate | 1000 ÷ 500 × 1 = 2 tablets |
📖 Worked Example — Liquid
| Step | Action |
|---|---|
| Order | Amoxicillin 250 mg PO · On hand: 125 mg / 5 mL |
| Identify | D = 250 mg · H = 125 mg · Q = 5 mL |
| Calculate | 250 ÷ 125 × 5 = 10 mL |
Method 2 — Dimensional Analysis DA Preferred
DA is just multiplying fractions while canceling units like a chain. Wrong units won't cancel — you'll catch the error immediately.
The DA Rule: Set up fractions so the units you don't want cancel top-to-bottom, and the unit you do want survives at the end.
📖 Worked Example — Conversion Needed
| Step | Action |
|---|---|
| Order | Ibuprofen 0.6 g PO · On hand: 200 mg / 5 mL |
| DA Chain | (0.6 g / 1) × (1000 mg / 1 g) × (5 mL / 200 mg) = 15 mL |
| Check | g cancels g · mg cancels mg · only mL remains ✓ |
Dosage by Weight (kg-Based)
Used when the order is written as mg/kg or mcg/kg. Common in pediatrics. Always convert lbs → kg first if needed (÷ 2.2).
The Process — Always 2 Parts
| Step | Action |
|---|---|
| Step 1 | Find the Patient's Dose — Multiply ordered dose (mg/kg) × patient's weight in kg → total dose needed |
| Step 2 | Calculate How Much to Give — Use D/H × Q or DA to find volume/tablets |
DA All-in-One Chain
(Weight kg / 1) × (mg ordered / 1 kg) × (mL or tabs / mg on hand) = mL to give
Worked Examples
Example 1 — Weight in kg
| Step | Action |
|---|---|
| Order | 20 kg child · Amoxicillin 25 mg/kg · On hand: 250 mg/5 mL |
| Step 1 | 20 kg × 25 mg/kg = 500 mg needed |
| Step 2 | 500 ÷ 250 × 5 = 10 mL |
Example 2 — Weight in lbs (Full DA Chain)
| Step | Action |
|---|---|
| Order | 44 lbs patient · Amoxicillin 25 mg/kg · On hand: 250 mg/5 mL |
| DA Chain | (44 lb/1) × (1 kg/2.2 lb) × (25 mg/1 kg) × (5 mL/250 mg) = 10 mL |
| Steps shown | 44 ÷ 2.2 = 20 kg · 20 × 25 = 500 mg · 500 ÷ 250 × 5 = 10 mL |
Safe Dose Range Check Always Verify
Some problems give a safe dose range (e.g., 10–15 mg/kg/day). You must check if the ordered dose falls within that range.
| Step | Action |
|---|---|
| Min dose | Low end (mg/kg) × patient's weight |
| Max dose | High end (mg/kg) × patient's weight |
| Compare | Min ≤ Ordered ≤ Max → ✅ Safe · Outside range → ⚠️ Hold and clarify |
Never skip the safe dose check on NCLEX or clinical exams — it's often a separate question and a real patient safety step.
Powdered (Reconstituted) Medications
Some oral drugs come as a dry powder and must be mixed with water (diluent) before use. You reconstitute first, then dose like a regular liquid.
The 3-Stage Approach
| Stage | Action |
|---|---|
| 1 | Read the label — It tells you exactly how much diluent (water) to add. Always follow exactly. |
| 2 | Determine final concentration — After mixing, note the resulting concentration (e.g., 250 mg/5 mL). This is your Have (H). |
| 3 | Calculate dose — Use D/H × Q or DA exactly like a regular liquid oral medication. |
Worked Examples
Example 1 — Powder Reconstitution + Dose Calc
| Step | Action |
|---|---|
| On hand | Amoxicillin powder. Label: "Add 78 mL water → 100 mL suspension (200 mg/5 mL)" |
| Order | Amoxicillin 400 mg PO q8h |
| Reconstitute | Add 78 mL water → 200 mg/5 mL suspension ✓ |
| Identify | D = 400 mg · H = 200 mg · Q = 5 mL |
| Calculate | 400 ÷ 200 × 5 = 10 mL per dose |
Example 2 — Powder + Weight-Based + DA Chain
| Step | Action |
|---|---|
| Patient | 33 lbs · Order: Azithromycin 10 mg/kg PO once |
| On hand | After reconstitution: 100 mg/5 mL |
| DA Chain | (33 lb/1) × (1 kg/2.2 lb) × (10 mg/1 kg) × (5 mL/100 mg) = 7.5 mL |
| Steps shown | 33 ÷ 2.2 = 15 kg · 15 × 10 = 150 mg · 150 ÷ 100 × 5 = 7.5 mL |
Key Points for Powder Meds
| Rule | Why It Matters |
|---|---|
| Never add more or less diluent than stated | Changes the concentration — every dose will be wrong |
| Check expiration after mixing | Most oral suspensions expire 7–14 days after reconstitution and must be refrigerated |
| Shake well before each use | Powder suspensions settle — an unshaken dose may be mostly water |
| Label the bottle with date/time of mixing | Nursing responsibility and a common NCLEX point |
Step-by-Step Practice Calculator
Enter your values. The calculator shows you the full DA setup — not just the answer.
Oral Medication Calculator
Dosage by Weight Calculator
D · H · Q — The Three You Always Identify First
D=Desired (ordered)
H=Have (on hand)
Q=Quantity
Essential Conversions
| From → To | Conversion |
|---|---|
| g → mg | × 1000 (1 g = 1000 mg) |
| mg → g | ÷ 1000 |
| mg → mcg | × 1000 (1 mg = 1000 mcg) |
| mcg → mg | ÷ 1000 |
| lb → kg | ÷ 2.2 (1 kg = 2.2 lb) |
| kg → lb | × 2.2 |
| tsp → mL | × 5 (1 tsp = 5 mL) |
| tbsp → mL | × 15 (1 tbsp = 15 mL) |
When to Use Which Method
| Situation | Best Method |
|---|---|
| Same units, no conversion | D/H × Q (fast) |
| Unit conversion needed | Dimensional Analysis |
| Weight-based, simple | 2-step: find dose → D/H×Q |
| Weight-based, lbs | Full DA chain (lb→kg→mg→mL) |
| Powder med | Reconstitute first → then DA |
| Safe dose range check | Always separate step |
Common Rounding Rules
| Medication Type | Round To |
|---|---|
| Tablets | Nearest ½ tablet (e.g. 1.5 tab) |
| Oral liquids (adult) | Nearest tenth (0.1 mL) |
| Pediatric liquids | Nearest hundredth (0.01 mL) |
| Weight (lb → kg) | Nearest tenth kg |
DA Setup Reminders
Golden Rule of DA: The unit you want to cancel goes diagonally (top of one fraction, bottom of the next). The unit you want to keep stands alone at the end.
Quick Check: Cross out matching units across fractions. If only the answer unit remains → you're good. If a wrong unit is left over → flip a fraction and try again.