Medical vs surgical asepsis: clean and sterile technique for nurses

Medical asepsis, or clean technique, reduces the number of microorganisms and stops them spreading. Surgical asepsis, or sterile technique, removes every microorganism from an area and keeps it that way. Use clean technique for routine care and sterile technique when you enter a body area that is normally sterile.

Sources checked 18 October 2026.

Medical and surgical asepsis

Asepsis means the absence of disease-causing microorganisms. In practice it is the set of actions that keep them away from the client. Open RN describes medical asepsis as a protective barrier against pathogens, and surgical asepsis as a purposeful attack on every microorganism in and around a sterile field.

Side by side

Which procedures need which

• Clean technique: bathing, oral care, giving oral medications, taking vital signs, nasogastric tube feeding, emptying a urinary drainage bag, and most care under standard and transmission-based precautions.
• Sterile technique: surgical procedures, invasive wound management, central line care and dressing changes, and inserting an indwelling urinary catheter in an acute care hospital.

CDC accepts clean technique for intermittent catheterization outside acute care, for example a client who catheterizes at home. Exam questions set in a hospital expect sterile technique for any urinary catheter insertion.

IV starts and injections use aseptic non-touch technique: you never touch key parts such as the needle, the syringe tip or the prepared site. Your facility decides whether a given procedure needs sterile or clean gloves.

Sterile field rules

Open RN lists these parts of a sterile field as contaminated:

• Anything within 1 inch (2.5 cm) of the edge.
• Any part that hangs below the surface of the table.
• Anything below waist level or above shoulder level.
• A field or supplies you have not watched the whole time, for example if you turned away or left the room.
• Anything within 1 inch of a hole, a tear or moisture that has soaked through from an unsterile surface.

And these actions keep it sterile:

• Check every package for damage, moisture, expiry and the sterilization indicator before you open it.
• Open a sterile kit away from your body first, then the sides, and the flap nearest you last.
• Do not reach across the field. Keep your arms and body from passing over it.
• Drop items onto the field from about 6 inches away. Pour solutions from the side, without splashing.
• Only sterile items touch sterile items.

Hand hygiene

Hand hygiene underpins both kinds of asepsis. CDC prefers an alcohol-based hand rub for most clinical care. Wash with soap and water when your hands are visibly soiled. For Clostridioides difficile, most nursing courses and Open RN teach soap and water after care, because alcohol does not reliably kill the spores. CDC also asks for soap and water after care during C. difficile outbreaks, and puts gloves and gowns first. Gloves never replace hand hygiene.

How to remember it

• Medical asepsis minimizes. Surgical asepsis eliminates.
• Sterile touches sterile. Clean touches clean. When one touches the other, both are clean, not sterile.
• Waist to shoulders, in your sight. That is the only sterile zone.

Other safety pages: RACE and PASS fire safety, code blue and hospital emergency codes, and isolation precautions in nursing mnemonics.

Practice questions

1. Question 1Multiple choiceSafety and Infection Control
   In an acute care hospital, which procedure requires surgical asepsis?

   Inserting an indwelling urinary catheterGiving an oral medicationGiving a bed bathChecking a tube feeding residual
   Check answer
2. Question 2Multiple responseSafety and Infection Control
   A nurse has set up a sterile field on a bedside table. Which parts of the field are considered contaminated? Select all that apply.

   The outer 1 inch (2.5 cm) of the drapeThe part of the drape hanging below the tabletopA field the nurse turned away from to answer the phoneAn area near a damp patch that has soaked through from the tableThe centre of the drape, held at waist level
   Check answer
3. Question 3Multiple choiceSafety and Infection Control
   How should the nurse add a sterile solution to a sterile bowl on a sterile field?

   Pour from the side of the field, holding the bottle about 6 inches above the bowl without splashing.Reach across the field and pour from directly above it.Rest the bottle lip on the bowl while pouring.Pour quickly so the field is exposed for less time.
   Check answer
4. Question 4Multiple choiceSafety and Infection Control
   A client has Clostridioides difficile infection. Which practice do nursing courses teach after care of this client?

   Remove gloves and gown, then wash hands with soap and water.Use alcohol-based hand rub only.Skip hand hygiene because gloves were worn.Put on sterile gloves for all care.
   Check answer