Oral and Injectable Doses
Tablets, liquids, injections and weight-based doses
Worked examples
| Order | Available | Setup | Answer |
|---|---|---|---|
| Metoprolol 50 mg PO | 25 mg tablets | 50 ÷ 25 × 1 | 2 tablets |
| Levothyroxine 0.1 mg PO | 50 mcg tablets | 0.1 mg = 100 mcg; 100 ÷ 50 | 2 tablets |
| Amoxicillin 500 mg PO | 250 mg/5 mL | 500 ÷ 250 × 5 | 10 mL |
| Heparin 5,000 units SC | 10,000 units/mL | 5,000 ÷ 10,000 × 1 | 0.5 mL |
| Morphine 3 mg IV | 4 mg/mL | 3 ÷ 4 × 1 | 0.75 mL |
| Furosemide 40 mg IV | 10 mg/mL | 40 ÷ 10 × 1 | 4 mL |
| Enoxaparin 1 mg/kg SC, patient 80 kg | 100 mg/mL | 80 mg ÷ 100 × 1 | 0.8 mL |
Weight-based doses: steps
- Convert weight to kg (lb ÷ 2.2).
- Multiply by the ordered mg/kg → dose.
- Check whether the order is per dose or per day (divide daily doses by the number of doses).
- Convert the dose to volume or tablets.
Example: vancomycin 15 mg/kg IV, patient 154 lb → 70 kg × 15 = 1,050 mg.
Reconstituting powders
- Read the label: which diluent and how much.
- Note the resulting concentration (e.g., "adding 4.8 mL gives 100 mg/mL").
- Label multi-dose vials with date, time, concentration and your initials.
Example: vial makes 100 mg/mL; order 250 mg → 250 ÷ 100 = 2.5 mL.
Injection basics
| Route | Angle | Needle (adult, typical) | Notes |
|---|---|---|---|
| Intradermal | 10–15° | 25–27 G, ⅜–⅝ in | Forms a bleb (TB skin test); don't massage |
| Subcutaneous | 45–90° | 25–30 G, ⅜–⅝ in | 45° if little fat; insulin and heparin: don't massage; don't aspirate |
| Intramuscular | 90° | 22–25 G, 1–1½ in | Ventrogluteal preferred site for larger volumes (up to ~3 mL); deltoid ≤1 mL; vastus lateralis for infants |
Z-track (irritating drugs): pull skin aside, inject, wait 10 sec, release. Insulin: use a U-100 insulin syringe; dose in units (no calculation of mL needed).
Priority
An answer that seems odd (e.g., 8 tablets, or 15 mL for an IV push) usually means a unit error. Recheck before giving, and ask a second nurse to double-check high-alert drugs.