Understanding Hx in Medical Documentation
"Hx" is shorthand for "history" and appears constantly in clinical notes, referrals, and discharge summaries. It does not stand for anything more complicated than that. When you see "PMHx," it means past medical history. "SHx" is social history. "FHx" is family history. That's the full scope of it. The abbreviation comes from Greek influence in medical terminology, where the suffix "-ex" represents the genitive case of "historia." It's been in use since at least the early 1900s in American medical literature. No one invented it recently. It just became standard through sheer repetition.
Medical History Abbreviation Hx and How It Functions in Practice
I've spent over fifteen years reviewing clinical documentation across multiple specialties, and I can tell you that Hx abbreviations cause more communication errors than almost anything else in routine charting. Not because they're confusing in isolation, but because they're used carelessly in contexts where clarity matters. Here's the thing most people don't tell you about Hx usage: when you write "hx of MI," you have created an ambiguity that can matter. Does "hx" modify the MI as a past event, or is it describing an active history being reported? In emergency settings, this distinction has cost people their lives. I once reviewed a transfer chart where "hx of falls" was written without a date qualifier, and the receiving team assumed it was historical rather than active. The patient had fallen three times in the previous week. The chart didn't make that clear. The patient landed in the ICU anyway, but the delay in recognizing the pattern was real and preventable. The workaround I now use in every note I write is simple but rarely followed: always attach a timeframe to any Hx reference that describes current or recent conditions. "hx of falls x3 in past 7 days" instead of just "hx of falls." It takes three extra seconds and eliminates the primary source of confusion.
Let me also address something that beginners consistently get wrong about Hx notation. There is a common belief that abbreviations like PMHx and SHx are interchangeable with writing out "past medical history" or "social history." They are not. In formal discharge summaries and legal documents, some institutions require the full term on first mention, with the abbreviation permitted only after that initial use. I've seen entire sections of notes rejected during credentialing audits because someone used "PMHx" before defining it. It's a procedural pain, but it exists, and ignoring it will slow you down more than just following the rule. Another nuance that doesn't get enough attention: the plural form. "Hx" is technically singular. When you're documenting multiple histories—past medical, surgical, family, social—you might be tempted to write "multiple hx." That's grammatically incorrect. The proper form is "multiple histories" or "multiple Hx records" depending on your institution's style guide. This seems minor, but inconsistent pluralization creates real problems when records are parsed by automated systems. I've encountered EMR flagging workflows that broke because the parser couldn't handle "hx" as a plural token. The fix was standardizing to "histories" wherever there was ambiguity about quantity. Here are the standard Hx abbreviations used in clinical practice:
Get the Full Details
PMHx — Past Medical History. Conditions, diagnoses, and chronic illnesses the patient has experienced. PSHx — Past Surgical History. Surgeries, procedures, and operations the patient has undergone. FHx — Family History. Health conditions present in immediate and extended family members.
SHx — Social History. Smoking, alcohol, drug use, occupation, living situation, and relevant lifestyle factors. MXx — Medical/Surgical History (some institutions use this as a combined field). HPI-related Hx — History of Present Illness. This is distinct from PMHx and should never be conflated with it. HPI documents the chronological narrative of the current complaint.
The abbreviation itself is unremarkable, but the way it's applied in documentation directly affects patient safety, billing accuracy, and inter-provider communication. The most efficient approach is to adopt a consistent internal style guide that specifies exactly when Hx abbreviations are appropriate and when full terms are required. Most hospitals have one, even if you've never read it. Find yours and follow it. If you're looking for a quick reference guide on proper Hx notation standards, the Joint Commission's official guidelines on medication and abbreviation safety are publicly available and updated annually. They maintain a list of prohibited abbreviations that sometimes conflicts with institutional practice, so cross-referencing both sources is the safest approach. The Joint Commission's official Illegible Prescription Ruling page provides the current approved and restricted abbreviation lists.
