How long a shot takes to wear off depends entirely on what was injected. A dental numbing shot typically wears off in 1 to 4 hours, a cortisone shot provides relief for weeks to months before fading, and vaccine side effects usually resolve within a day or two. Below is a breakdown of the most common types of shots and what to expect as each one wears off.
Dental Numbing Shots
Dental injections use local anesthetics, most commonly lidocaine, to block pain signals in a specific area of your mouth. Without a vasoconstrictor (a chemical that narrows blood vessels to keep the drug concentrated locally), lidocaine wears off in about 30 to 120 minutes. Most dentists add epinephrine as a vasoconstrictor, which extends the numbing to 2 to 4 hours.
The type of tissue matters too. Harder tissues like teeth and bone lose numbness faster than soft tissues like your lips, cheeks, and tongue. That’s why you can sometimes feel your teeth again while your lower lip still feels swollen and tingly. The location of the injection plays a role as well: areas with more blood flow clear the anesthetic faster.
If you want the numbness to fade sooner, a few things can help. Gently massaging the numb area with clean fingers in circular motions stimulates blood flow and helps your body break down the anesthetic. Applying a warm, damp cloth to the outside of your cheek for 10 to 15 minutes dilates blood vessels and improves circulation. Light physical activity like a short walk also boosts overall circulation. Staying hydrated helps your body metabolize the drug more efficiently. Just be careful not to bite your cheek or tongue while sensation is still reduced.
Cortisone Shots for Joint Pain
Cortisone (corticosteroid) injections work differently from numbing shots. Instead of blocking nerve signals, they reduce inflammation in a joint or tendon. The relief typically lasts somewhere between a few weeks and a few months, though some people experience benefits for longer.
Don’t be alarmed if your pain gets worse in the first 24 to 48 hours after the injection. This temporary flare is a well-known reaction to the injection itself, not a sign that the shot didn’t work. The anti-inflammatory effect usually kicks in within a few days and then gradually tapers as your body clears the steroid from the area. Once the cortisone wears off, the underlying inflammation can return, which is why these shots are often used alongside physical therapy or other longer-term treatments rather than as standalone fixes.
Vaccine Side Effects
When people ask how long a vaccine shot takes to “wear off,” they usually mean how long the side effects last. Common reactions like muscle aches, fatigue, and low-grade fever typically resolve within a day or two. Soreness at the injection site on your arm can linger for several days but is rarely severe enough to limit daily activity.
The protective immune response, on the other hand, is the whole point and is designed to last much longer. That immunity builds over the following weeks and can persist for months or years depending on the vaccine.
Allergy Shots
Allergy immunotherapy works on a completely different timeline. These shots gradually train your immune system to tolerate allergens, and a full course takes three to five years of regular injections. The payoff is significant: about 60% of people who complete the full course experience permanent benefits even after stopping. For the other 40%, allergy symptoms may gradually return over a period of years.
Depo-Provera (Birth Control Shot)
The Depo-Provera contraceptive shot is designed to last about three months per dose, but its effects linger well beyond that window. After your last injection, it can take 10 months or more before ovulation returns. About 50% of people who stop Depo-Provera will conceive within 10 months, though individual timelines vary based on age, weight, and how long you were on the medication. One study found that the average time to resume ovulating was roughly five to six months for the lower dose and over seven months for the higher dose.
Weekly Weight Loss Injections
Medications like semaglutide (Ozempic, Wegovy) have a half-life of about seven days, meaning it takes roughly a week for your body to clear half of each dose. After stopping, the appetite-suppressing effects fade gradually over several weeks as the drug works its way out of your system. Most people notice hunger signals returning within the first week or two after their last injection, with the medication fully clearing over the following month or so.
Epinephrine (EpiPen)
Epinephrine injections for severe allergic reactions have a rapid onset but a very short duration. The effects wear off quickly, which is why an EpiPen is considered emergency supportive therapy, not a complete treatment. You should always seek immediate medical care after using one, because the allergic reaction can return (a phenomenon called a biphasic reaction) once the epinephrine fades. A second auto-injector may be needed if symptoms return before help arrives.
What Affects How Quickly Any Shot Wears Off
Several factors influence how fast your body processes an injected medication. Liver function is the biggest one, since most drugs are metabolized there. People with chronic liver conditions or advanced heart failure may clear medications more slowly. Genetic differences also play a role: variations in liver enzymes mean some people are naturally fast metabolizers while others are slow, which partly explains why the same injection can wear off in two hours for one person and four hours for another.
The injection site matters as well. Areas with rich blood supply absorb and clear medications faster than areas with less circulation. Body composition, age, and whether you’re taking other medications that compete for the same metabolic pathways can all shift the timeline in either direction. Infants and very young children process many drugs more slowly because their liver enzyme systems aren’t fully developed yet.