What it means
In older medication orders, hs or HS meant at bedtime, the hour of sleep. The same letters have also meant half-strength, as in a diluted feeding or solution. Because one could be read as the other, safety groups advise writing "at bedtime" or "half-strength" in full; ISMP's current list recommends "QHS" or "qhs" for bedtime. In other notes HS can stand for other things, such as heart sounds.
For the nurse
If an order uses HS and the meaning is not clear, clarify it with the prescriber. Write the full words in your own notes.