Expressing concentrations in metric units
When expressing concentrations in metric units, use a virgule in place of the word per when the following conditions have been met:
- the construction involves at least one metric unit of measure
- at least one element includes a specific numeric quantity
Units of measure should be abbreviated in accordance with the other rules in this section.
Hemoglobin level was 14 g/dL.
Blood volume was 70 mL/kg of body weight.
The drug dosage was 25 mg/d.
Do not use the virgule when any or all of the following conditions exist:
- a prepositional phrase intervenes between the two units of measure
- no specific numeric quantity is expressed
- in nontechnical expressions
The patient was given 3.5 mEq of potassium per liter.
Hemoglobin levels are reported in grams per deciliter.
She has symptoms 2 days per month.
Do not use a virgule when the units of measure are not related; i.e., they represent different units of measure, particularly in drug concentration expressions.
The patient was prescribed Advair 250 per 50 b.i.d.
The patient was given Hydro-Tussin? HD 200 mg per 10 mL.
If it can be confirmed that an expression is part of a legally registered trademark for a medication, express the concentration as indicated by the manufacturer.
She takes Diovan HCTZ 80/12.5 for blood pressure control.
I will start her on Nortrel 0.5/35 for birth control.
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