It depends entirely on the type of shot. A dental numbing injection wears off in 1 to 8 hours, a cortisone shot provides relief that fades over weeks to months, and a contraceptive shot lasts about 13 weeks. Because “shot” covers so many different injections, here’s a breakdown of the most common ones people wonder about.
Dental Numbing Shots
This is one of the most frequently searched types, and for good reason: few things are more annoying than a numb lip hours after a filling. Local anesthesia at the dentist typically wears off within 1 to 8 hours, depending on the procedure and the specific drug used.
For a routine filling, expect numbness to fade in 1 to 3 hours. Simple tooth extractions and root canals keep you numb longer, usually 3 to 5 hours. Complex oral surgeries can leave you numb for 6 to 8 hours or more. The anesthetic itself matters too. Lidocaine, the most common option, lasts about 1 to 2 hours. Articaine, often chosen for deeper procedures, lasts 3 to 5 hours.
Blood flow to the injection site plays a role in how quickly the drug clears your system. Areas with more blood supply tend to process the anesthetic faster. Physical activity can also speed things up slightly by increasing circulation, which is why your dentist may tell you to take it easy if you want to avoid biting your cheek before the numbness fades.
Cortisone Shots for Joint Pain
Cortisone (corticosteroid) injections work differently from numbing shots. They don’t wear off the way an anesthetic does. Instead, they reduce inflammation over a period of days, with the relief gradually tapering weeks or months later.
Most people start feeling relief within a few days. In a study of 140 patients receiving musculoskeletal steroid injections, half reported pain relief by day 3, and 95% had relief within 8 days. About 1 in 5 patients experienced a temporary pain flare after the injection, which delayed relief by roughly a day and a half on average.
The relief itself typically lasts anywhere from several weeks to a few months, varying by the joint, the severity of inflammation, and individual factors. When the anti-inflammatory effect fades, pain gradually returns rather than coming back all at once.
Epidural and Spinal Blocks
If you’ve had an epidural for labor, surgery, or a procedure, numbness and leg heaviness typically wear off within a few hours after the last dose. Single-injection epidurals tend to clear faster than catheter-based ones, where medication was delivered continuously. In either case, you’ll need to stay in bed until you can move your legs and bear weight safely. Most people regain full sensation and motor control within 2 to 4 hours, though the exact timeline varies with the drugs used and how long the epidural was running.
Contraceptive Shots
The birth control shot (Depo-Provera) is designed to last 13 weeks, or about 3 months. You need your next injection right at that 13-week mark to maintain continuous protection. If you go past 15 weeks between shots, you may need a pregnancy test before the next one and should use a backup method of birth control for 7 days afterward.
After stopping the shot entirely, it can take longer for fertility to return than with other birth control methods. Some people ovulate again within a few months, but for others it can take 6 to 10 months or occasionally longer before regular cycles resume.
Weight Loss Medication Shots
Weekly injectable weight loss medications like semaglutide have a half-life of about one week, meaning half the drug is still in your system 7 days after your dose. This is why they’re given once weekly. After you stop taking the medication entirely, it takes roughly 4 to 5 weeks for it to fully clear your body. Appetite suppression tends to fade gradually during that window, and many people notice increased hunger returning within a few weeks of their last injection.
Botox and Cosmetic Injections
Botox and similar neurotoxin injections take the longest to wear off of any common shot. After injection, initial muscle weakening doesn’t begin for several days, and the peak effect takes several weeks to develop. The effects start fading around 2 months, and normal muscle movement generally returns by 3 months. This is why cosmetic treatments are typically scheduled every 3 to 4 months to maintain results.
Epinephrine (EpiPen)
Epinephrine for allergic reactions works fast but wears off fast. It has a rapid onset and a short duration of action, with effects lasting roughly 15 to 20 minutes. The drug is rapidly broken down in the body, which is why people experiencing anaphylaxis need emergency medical care even after using an auto-injector. A single dose buys time but does not resolve the reaction on its own.
Vaccine Side Effects
Vaccines aren’t meant to “wear off” in the way other shots do, since their purpose is a lasting immune response. But the side effects people associate with getting a shot, like a sore arm, fatigue, or low-grade fever, are temporary. Most side effects are mild and resolve within a few days. The shingles vaccine, known for causing more noticeable soreness and fatigue than many other vaccines, typically produces symptoms that clear in 2 to 3 days.
What Affects How Quickly Any Shot Wears Off
Several biological factors influence how fast your body processes an injected medication. Blood flow at the injection site is one of the biggest: areas with rich blood supply absorb and clear drugs faster. Your metabolism, age, and overall health status also play a role. Younger, more physically active people tend to metabolize drugs more quickly. The specific formulation of the drug matters too, since some injectables are deliberately designed to release slowly over days or weeks.
The injection site itself can change things. A shot in a highly vascular area like the deltoid muscle clears faster than one deposited into fatty tissue or a joint capsule, where blood flow is lower and the drug lingers longer. This is by design for medications like cortisone or contraceptives, where a slow, sustained release is the whole point.