Inserting a urinary catheter (often called “installing” one) is a sterile medical procedure that involves threading a thin, flexible tube through the urethra and into the bladder to drain urine. The process differs depending on anatomy, but the core principles are the same: maintain a completely sterile technique, use proper lubrication, and advance the catheter gently until urine flows. Whether you’re a nursing student learning the skill, a caregiver assisting at home, or someone preparing for self-catheterization, understanding each step helps prevent complications like infection or tissue injury.
Choosing the Right Catheter Size
Catheters are measured in French (Fr) units, where each French unit equals one-third of a millimeter in outer diameter. A 14 Fr catheter, for example, has a diameter of about 4.7 mm. Most adult women use sizes ranging from 12 to 16 Fr. Most adult men use sizes between 14 and 18 Fr, though some need up to 24 Fr. Using too large a catheter causes unnecessary discomfort; too small and it may not drain properly. The size is typically chosen by a healthcare provider based on the patient’s anatomy and the reason for catheterization.
Gathering Supplies and Preparing the Field
Before touching anything, wash your hands thoroughly and open a sterile catheter kit on a clean surface within easy reach. A standard kit includes the catheter, a collection bag, sterile gloves, antiseptic swabs (usually povidone-iodine), lubricant, a syringe pre-filled with sterile water, and sterile drapes. Attach the catheter to the drainage collection system before you begin, and don’t break that sealed connection unless you need to swap the catheter itself.
Test the retention balloon before insertion by inflating it with the syringe of sterile water, checking for leaks, then deflating it. Apply a generous amount of lubricant to the catheter tip. Place all supplies so you can reach them without turning away from the patient or crossing over sterile areas.
Insertion in Males
Position the patient lying flat on their back with hips comfortably apart. Place a sterile drape with a hole (fenestrated drape) over the pelvis so only the penis is exposed.
With your non-dominant hand, hold the shaft of the penis straight and upright. If the patient is uncircumcised, retract the foreskin. This hand is now considered non-sterile for the rest of the procedure and must stay on the penis without touching any equipment. With your other hand, clean the head of the penis using antiseptic-soaked swabs in a circular motion, starting at the urethral opening and wiping outward.
If a local anesthetic is being used, insert the tip of the lidocaine syringe into the urethral opening and inject about 5 mL, then pinch the opening closed for at least one minute. The anesthetic both numbs and gently stretches the urethra, making catheter passage easier.
With your sterile hand, advance the lubricated catheter slowly through the urethra. Keep the penis held straight upward to smooth out the natural curve of the male urethra. If you feel resistance around the level of the prostate, ask the patient to take slow, deep breaths or cough gently while you apply steady, light pressure. This relaxes the external sphincter and usually allows the catheter to pass. If significant resistance continues, stop. Forcing the catheter can cause serious injury.
Continue advancing the catheter all the way to its base (the side port) before inflating the balloon. This is critical because inflating the balloon while it’s still in the prostate or urethra causes significant bleeding and pain. Once the catheter is fully advanced and urine is flowing, slowly inflate the balloon with 5 to 10 mL of sterile water. If the patient reports sharp pain or you feel obvious resistance during inflation, deflate immediately, advance the catheter further, and try again.
Insertion in Females
Position the patient lying on their back with knees bent, feet flat on the bed, and hips apart (sometimes called the frog-leg position). Place the sterile drape so the vulva is exposed. The urethral opening in women sits as a small slit about 2.5 cm below the clitoris and just above the vaginal opening. In older women, the opening can recede slightly into the vagina. If it’s hard to see, you can often feel it in the midline as a soft mound surrounded by a firmer ring of tissue.
With your non-dominant hand, gently spread the labia to expose the urethral opening. This hand is now non-sterile and must remain in place for the rest of the procedure. Clean around the opening with antiseptic swabs using a circular motion, starting at the meatus and wiping outward.
With your free hand, gently pass the lubricated catheter into the urethra. The female urethra is much shorter than the male urethra, so you won’t need to advance it nearly as far. Urine should begin flowing into the collection tubing once the tip reaches the bladder. If the catheter accidentally enters the vagina, discard it and use a new one. Inflate the balloon with the recommended volume, typically 10 mL of sterile water, then gently pull back on the catheter until you feel it seat snugly against the bladder neck.
Why Sterile Water, Not Saline
Always inflate the catheter balloon with sterile water, never normal saline. Over time, water naturally seeps out of the balloon through osmosis. If saline is inside, this water loss concentrates the salt, and salt crystals can form and block the inflation channel. When it comes time to remove the catheter, the balloon won’t deflate, creating a painful and complicated situation that may require medical intervention to resolve.
When Not to Insert a Catheter
Blood visible at the urethral opening is the single most important warning sign that the urethra may be injured. In males especially, inserting a catheter through a damaged urethra can turn a partial tear into a complete one. If there’s any suspicion of urethral trauma, such as after a pelvic fracture or straddle injury, catheter insertion should wait until imaging confirms the urethra is intact. Other signs that call for caution include inability to pass the catheter despite proper technique, visible swelling or bruising around the genitals, or a patient who reports severe pain beyond normal discomfort.
Positioning the Drainage Bag
Once the catheter is in place, the drainage bag must always hang below the level of the bladder. This prevents urine from flowing backward into the bladder, which is one of the fastest routes to a catheter-associated urinary tract infection. When the patient is walking, hold the tubing with the bag below the hips. When lying in bed, hang the bag on the side of the bed frame, never on the floor. The patient can sleep in any position as long as the bag stays below bladder level.
During the day, a smaller leg bag strapped to the thigh or calf works well for mobility. It should always sit below the waist. When emptying either type of bag, keep it lower than hip level throughout the process to avoid backflow.
Reducing Infection Risk
Catheter-associated urinary tract infections are among the most common healthcare-acquired infections, and most are preventable. The CDC’s prevention guidelines emphasize a few straightforward principles: only insert a catheter when truly necessary, remove it as soon as possible, maintain a closed drainage system (don’t disconnect the catheter from the bag), and use strict sterile technique during insertion. Every extra day a catheter stays in place increases infection risk, so regular reassessment of whether the catheter is still needed is one of the most effective protective measures.
Daily cleaning around the catheter site with soap and water, keeping the drainage bag off the floor, and washing hands before and after handling any part of the system all reduce bacterial entry. Avoid routine irrigation or flushing of the catheter unless a healthcare provider specifically recommends it for a blockage.