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 lasting weeks to months, and vaccine side effects usually fade within 2 to 3 days. Below is a breakdown of the most common types of shots and what to expect from each.
Dental Numbing Shots
Dental anesthesia is the most common reason people search this question, usually because they’re sitting in a car after a filling wondering when they can eat again. The answer depends on which anesthetic your dentist used and whether it included epinephrine, a chemical that constricts blood vessels and keeps the numbing agent in place longer.
Lidocaine, the most widely used dental anesthetic, lasts 30 minutes to 2 hours on its own. When combined with epinephrine (which is standard practice), that extends to 2 to 4 hours. Articaine, another common choice, lasts 1 to roughly 4 hours with epinephrine. Bupivacaine is reserved for procedures that need longer-lasting numbness: 2 to 3 hours alone, and 3 to 8 hours with epinephrine.
The numbness you feel in your lip and cheek (soft tissue numbness) always outlasts the deeper tooth-level numbness. So even after the treated tooth has regained feeling, your lip may still feel swollen and tingly for another hour or two. Avoid chewing on the numb side until full sensation returns, since you can easily bite your cheek or tongue without realizing it.
Why Some People Stay Numb Longer
Several factors affect how quickly your body clears a local anesthetic. Areas with more blood flow absorb the drug faster, which is why shots in the gums near the front of the mouth tend to wear off sooner than those given for back molars. The dose matters too: a deeper procedure requiring more anesthetic will keep you numb longer. Individual metabolism plays a role as well. People with faster circulation or higher enzyme activity will process the drug more quickly, while others may feel lingering numbness for several hours.
Cortisone Shots for Joint Pain
Cortisone (corticosteroid) injections work on a completely different timeline than numbing shots. Rather than wearing off in hours, the goal is for them to last as long as possible. Relief typically begins about a week after injection and lasts anywhere from a few weeks to a few months.
The first 24 to 48 hours can actually feel worse, not better. A temporary flare of pain and swelling at the injection site is common before the anti-inflammatory effects kick in. Once the shot takes full effect, you can expect reduced pain and improved mobility in the treated joint. When the cortisone does wear off, pain tends to return gradually rather than all at once. Most people can tell the shot is fading when they start noticing stiffness or soreness creeping back during activities that had been comfortable.
Botox and Dysport
Cosmetic neurotoxin injections like Botox and Dysport don’t “wear off” in the way a numbing shot does. Instead, they gradually lose their effect over months as your body regenerates the nerve signals that the injection temporarily blocked.
Dysport tends to kick in faster, with visible results in 2 to 3 days and peak smoothing around the two-week mark. Botox is slightly slower, typically taking 4 to 7 days before changes become noticeable. Both last 3 to 4 months on average. You’ll notice movement gradually returning to the treated area as the effect fades, and most people schedule their next appointment when they see lines starting to reappear at rest.
Vaccine Side Effects
If you’re wondering how long you’ll feel lousy after a flu shot, COVID booster, or other vaccination, the answer is usually 2 to 3 days. Common side effects include soreness at the injection site, low-grade fever, fatigue, and body aches. These are signs your immune system is responding to the vaccine, not signs that something is wrong.
Arm soreness is almost always the first symptom to appear (within hours) and the last to fully resolve. Fever and fatigue, if they show up at all, tend to peak on the first or second day and clear by day three. The shingles vaccine is known for producing more noticeable side effects than most, but even those typically resolve within 2 to 3 days.
Epinephrine Auto-Injectors
Epinephrine from an EpiPen or similar device works fast, reaching peak levels in about 8 minutes when injected into muscle. But the effect is short-lived. The drug wears off relatively quickly, which is exactly why you need emergency medical care even if you feel better after using one.
Allergic reactions can return after the epinephrine fades. Most of these “biphasic” reactions happen within 4 to 6 hours, which is why hospitals typically observe patients for at least that long after treating anaphylaxis. In rare cases, symptoms can recur up to 24 to 72 hours later. An auto-injector is a bridge to emergency care, not a complete treatment on its own.
GLP-1 Weight Loss Injections
Weekly injections used for weight loss and blood sugar management, such as tirzepatide (Mounjaro, Zepbound), stay active in your system much longer than you might expect. Tirzepatide has a half-life of about 5 days, meaning half the drug is still circulating nearly a week after injection. After your last dose, it takes roughly 30 days for the medication to fully clear your body.
This long clearance time means that both the benefits and the side effects (nausea, reduced appetite, slower digestion) taper gradually over several weeks after stopping. You won’t feel a sudden change the day after a missed dose. If you’re discontinuing one of these medications, the transition is slow enough that your appetite and blood sugar levels shift over the course of a month rather than overnight.