A lidocaine injection typically numbs the area for about 1 to 2 hours when used on its own. When combined with epinephrine (a common additive that constricts blood vessels), the numbing effect can last roughly 2 to 3 hours or longer. The exact duration depends on the concentration used, where the injection is placed, and the formulation your provider chooses.
Onset and Typical Duration
Lidocaine is one of the fastest-acting local anesthetics. When injected as a 2% solution without any additives, numbness begins within about 1 minute and lasts an average of 100 minutes, or just over an hour and a half. That’s the duration measured in controlled studies of plain lidocaine used for hand surgery.
Most people notice the numbness fading gradually rather than all at once. You’ll typically feel tingling or a “pins and needles” sensation as normal feeling returns. Full sensation usually comes back within 2 to 3 hours of the injection, though the timeline shifts depending on the factors below.
How Epinephrine Extends the Effect
Many lidocaine injections include epinephrine, which tightens blood vessels around the injection site. This slows the rate at which your body absorbs the lidocaine, keeping it concentrated in the tissue longer. In one study comparing formulations used in hand surgery, adding epinephrine nearly doubled the duration of numbness, from about 100 minutes to nearly 187 minutes (just over 3 hours).
The tradeoff is that epinephrine-containing solutions are significantly more acidic, roughly 1,000 times more acidic than your skin tissue. That acidity is one reason these injections can sting more going in. Some providers add a small amount of sodium bicarbonate to neutralize the solution, which reduces the pain of the injection without affecting how well the lidocaine works.
What Affects How Long It Lasts
Several factors influence whether your numbness lears closer to 1 hour or 3 hours:
- Injection site: Areas with more blood flow (like the face and mouth) absorb lidocaine faster, so numbness tends to wear off sooner. Areas with less blood supply hold onto the anesthetic longer.
- Concentration: Lidocaine comes in concentrations ranging from 0.5% to 2%. Higher concentrations kick in faster but don’t necessarily last longer. In fact, a lower-concentration solution combined with epinephrine often outlasts a higher-concentration plain solution.
- Tissue inflammation or infection: Infected or inflamed tissue is more acidic than normal tissue. Since lidocaine works best in a neutral-to-slightly-alkaline environment, inflammation can reduce both how quickly it takes effect and how long it lasts. This is why numbing an infected area sometimes feels less effective.
- Amount injected: Larger volumes spread across a wider area generally provide longer-lasting numbness, partly because there’s simply more of the drug to absorb.
Dental Injections vs. Skin Injections
If you’re getting lidocaine at the dentist, you can expect numbness in your lip, tongue, or cheek to last 1 to 2 hours for soft tissue, though the tooth itself may lose numbness a bit sooner. Dental injections often include epinephrine, which is why the lingering numb-lip feeling can persist well after you leave the office.
For skin procedures like mole removal, stitches, or biopsies, the numbing effect at the wound site typically lasts 1 to 3 hours depending on the formulation. You may feel some soreness as the lidocaine wears off, which is the underlying tissue responding to the procedure rather than a problem with the anesthetic itself.
How Your Body Clears Lidocaine
Lidocaine is processed primarily by the liver. Once it enters your bloodstream from the injection site, the body breaks it down into several byproducts that are filtered out through the kidneys. The local numbing effect wears off long before the drug is fully eliminated from your system, because what matters for numbness is the concentration at the injection site, not the total amount in your blood.
People with liver conditions may process lidocaine more slowly, which doesn’t usually change how long the numbness lasts at the injection site but can increase the risk of side effects if large doses are used. The maximum safe dose is 4.5 mg per kilogram of body weight for plain lidocaine (up to 300 mg total) and 7 mg per kilogram when epinephrine is included (up to 500 mg total).
What to Expect as It Wears Off
As lidocaine fades, you’ll notice sensation returning in stages. Light touch and pressure come back first, followed by sharper sensations like pinprick and temperature. Some people experience brief tingling or mild itching during this transition, which is normal.
If you had a procedure done while numb, be cautious with the area until full sensation returns. It’s easy to accidentally bite a numb lip after dental work or bump a numb finger without realizing it. Once feeling is fully back, any discomfort you notice is from the procedure itself rather than the injection.