Stitching a wound, formally called suturing, involves pulling the edges of a cut together with a needle and thread so the tissue can heal with minimal scarring and a lower risk of infection. The process follows a consistent sequence: clean the wound thoroughly, numb the area, place stitches at even intervals, tie secure knots, and protect the site while it heals. Whether you’re learning this skill for medical training or simply want to understand what happens when a wound gets closed, here’s how each step works.
Which Wounds Need Stitches
Not every cut requires suturing. Stitches are the preferred closure method for wounds that are deep enough to expose fat or muscle, have edges that won’t stay together on their own, or sit in areas under tension from movement. Cuts longer than about 2 centimeters, gaping wounds, and lacerations that bleed heavily after pressure all generally benefit from sutures.
Skin glue works for small to medium wounds with edges that line up easily and sit in low-tension areas. Staples are common on the scalp, where they create even tension across the wound. But for deep, long, or complex lacerations, sutures remain the standard because they allow precise control over how tightly and deeply tissue is pulled together.
Some wounds should not be stitched closed at all. Animal bites, especially cat bites, puncture wounds, and injuries to the hand carry a high infection risk. For these, the safer approach is thorough cleaning and leaving the wound open to drain. The same applies to people with diabetes or weakened immune systems, where trapping bacteria under closed skin can lead to serious complications.
Cleaning and Preparing the Wound
Proper irrigation is the single most important step before placing any stitches. The goal is to flush out dirt, bacteria, and debris so they aren’t sealed inside the wound. The standard method uses a large syringe (35 to 50 mL) attached to a 19-gauge tip, which generates about 25 to 40 PSI of pressure when you push the plunger firmly with both hands. That’s enough force to dislodge contaminants without damaging the tissue. Pressures above 70 PSI can injure healthy cells, so high-pressure devices like water jets are avoided.
The volume of fluid matters too. A widely used guideline calls for roughly 50 mL of saline per centimeter of wound length. A 5-centimeter cut, for example, would need about 250 mL of irrigation. Normal saline or clean water works well. The stream should be directed into and along the wound from multiple angles until the tissue looks visibly clean.
After irrigation, the wound edges are examined to make sure they’re viable. Any dead, crushed, or heavily contaminated tissue is trimmed away so only healthy edges remain. This gives the stitches clean tissue to hold and reduces the chance of infection.
Numbing the Area
Local anesthetic is injected directly into the skin around the wound before any needles go through tissue. The most common choice is lidocaine in concentrations between 0.5% and 2%. It’s injected into the subcutaneous layer, the fatty tissue just beneath the skin, using a small needle. The numbing effect kicks in within a minute or two.
When epinephrine is added to the lidocaine, it constricts blood vessels near the injection site, which reduces bleeding and makes the anesthetic last longer. The safe upper dose for lidocaine alone is roughly 4.5 mg per kilogram of body weight. With epinephrine added, that ceiling rises to about 7 mg per kilogram. For a 70-kilogram adult, that means up to around 300 mg without epinephrine or 500 mg with it.
The injection itself stings briefly. A common technique to reduce that pain is injecting slowly and entering through the wound edge rather than through intact skin.
Choosing the Right Suture Material
Sutures come in two broad categories: absorbable, which the body breaks down over time, and non-absorbable, which must be removed manually. Absorbable sutures are often used for deeper tissue layers or facial repairs in children, where removal would be difficult or distressing. Non-absorbable sutures, typically nylon or similar synthetics, are the standard for most skin closures.
The thread itself is either a single strand (monofilament) or multiple strands braided together. Monofilament slides through tissue more smoothly and harbors fewer bacteria. Braided sutures hold knots more securely but can wick bacteria into the wound.
Size is measured on a scale that counts backward: larger numbers with more zeros mean thinner thread. A 6-0 suture is finer than a 4-0. The face typically gets 5-0 or 6-0 sutures for minimal scarring. The scalp, chest, abdomen, and extremities use thicker 4-0 or 5-0 material to handle the greater tension in those areas.
Placing a Simple Interrupted Stitch
The simple interrupted suture is the most fundamental and widely used technique. Each stitch is independent, so if one fails or needs to be removed early, the rest still hold. Here’s the sequence:
- Load the needle. The curved needle is grasped about two-thirds of the way back from the tip using a needle holder (a locking clamp designed for suturing). Forceps are held in the other hand to manipulate the wound edges.
- Enter the skin. The needle enters the skin on one side of the wound about 3 to 5 millimeters from the edge. It should go in perpendicular to the skin surface, following the curve of the needle through the tissue and out the bottom of the wound.
- Cross to the other side. The needle is then driven up through the opposite wound edge at the same depth and the same distance from the edge, so both sides are mirror images. The goal is to catch equal amounts of tissue on each side, which ensures the edges line up evenly when tied.
- Tie the knot. The needle holder is used to wrap the long end of the thread around the instrument, then the short tail is grasped and pulled through the loop. This first throw is typically a double wrap (called a surgeon’s knot) to prevent the thread from loosening while you tie the second throw. The second throw is a single wrap pulled in the opposite direction, creating a secure square knot. Two or three additional single throws can be added for security.
- Cut and repeat. The thread is trimmed, leaving tails of a few millimeters. The next stitch goes 5 to 7 millimeters from the first, and the process repeats along the length of the wound.
The tension on each stitch should be just enough to bring the wound edges together without blanching the skin white. Over-tightening cuts off blood flow and creates worse scarring. The edges should sit slightly raised, or everted, rather than folded inward, because the tissue will flatten naturally as it heals.
How the Wound Heals After Closure
Once stitched, the wound moves through a predictable healing sequence. In the first few days, the body sends white blood cells to clear bacteria and debris, causing the redness and mild swelling you’d expect. This inflammatory phase peaks around day 7 in humans, then gradually subsides.
By the end of the first week, the proliferative phase is underway. Skin cells migrate across the wound gap, new blood vessels form, and specialized cells called fibroblasts begin producing collagen to rebuild structural strength. This is when the wound starts to feel firm and slightly raised.
The final remodeling phase lasts the longest. The initial collagen is gradually replaced with stronger, more organized fibers, and the scar matures, softens, and fades. This process continues for months to years. A sutured wound typically regains about 80% of the skin’s original tensile strength, but never fully returns to its pre-injury state.
When to Remove Stitches
Leaving stitches in too long increases scarring because the body starts to form scar tissue around the thread itself. Removing them too early risks the wound reopening. The timeline varies by location:
- Face and forehead: 5 days
- Scalp: 7 days
- Arms and legs: 7 to 10 days
- Chest and abdomen: 12 to 14 days
Facial stitches come out earliest because the face has an excellent blood supply and heals quickly. The trunk takes longest because skin there is under constant tension from breathing and movement. After removal, adhesive strips are often placed across the wound for another week to support the still-fragile scar.
Signs of Infection to Watch For
A mild amount of redness and swelling around stitches is normal in the first 48 hours. Infection becomes a concern when you notice increasing pain or tenderness that gets worse rather than better after the first few days, spreading redness beyond the wound edges, warmth radiating from the site, visible swelling that continues to grow, or thick, cloudy drainage (pus) coming from the wound. A fever above 38°C (100.4°F) alongside any of these signs suggests the infection may be spreading deeper into the tissue. Infections can develop anytime within the first 30 days after closure, so the wound needs monitoring well after the stitches come out.