The “mmHg” unit on every blood pressure reading comes directly from the original measuring devices, which literally used a column of mercury – invented in the late 19th century and refined around 1896.
Modern devices, digital or aneroid, haven’t needed actual mercury for a long time, but the unit of measurement stuck around anyway – a technical habit that outlived the technology that created it.
Separately, hypertension earned the nickname “the silent killer” precisely because it usually causes no visible symptoms at all, even while steadily raising the risk of stroke or heart attack.
It’s the kind of number you read without ever questioning it, even though it comes from a lab more than a century old.
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