A fast or pounding heartbeat in the minutes after a dental injection often comes from one of two things: the small amount of adrenaline added to many dental anaesthetics, or the body's own stress response to the needle and the appointment. It can be a mix of both. In small studies of healthy adults, the smaller dose of adrenaline tested raised heart rate by a few beats a minute, while larger rises were seen with a bigger dose of adrenaline and with injections into the bone. True allergy to dental anaesthetic is rare. If palpitations come with chest pain, shortness of breath, dizziness or fainting, call triple zero (000).
Why the heart can speed up in the dental chair
Adrenaline in the anaesthetic
Many dental local anaesthetics contain a little adrenaline. It narrows the blood vessels near the injection, which lowers the amount of anaesthetic reaching the bloodstream and helps the numbness last longer and work better (Sisk, Anesthesia Progress, 1992). Some of the adrenaline is still absorbed into the bloodstream, where it can make the heart beat faster.
Knoll-Köhler and colleagues (Journal of Dental Research, 1989) measured this in 12 dental student volunteers given an injection in the upper front of the mouth. With 20 micrograms of adrenaline, heart rate rose by about 4 beats a minute just under three minutes after the injection. A dose four times higher (80 micrograms) raised it by 5 beats a minute from two minutes after the injection, rising to 13 beats a minute by the end of the 15 minutes they watched. The same anaesthetic without adrenaline caused no significant change.
Nerves and the injection itself
Anxiety is linked to a faster heart rate too. Liau and colleagues (Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontics, 2008) monitored 180 adults having a lower jaw injection before an extraction. Everyone received the same dose, yet people with severe dental anxiety had a significantly greater rise in heart rate during the injection, and pain from the injection was also linked to a higher heart rate. A study of 100 men in India (Sharma and colleagues, Journal of Maxillofacial and Oral Surgery, 2019) found a similar pattern.
So two people can receive identical injections and respond quite differently. A racing heart during or after the injection can come from adrenaline, from nerves or from both.
When some anaesthetic enters a blood vessel
The area around the lower jaw nerve has many blood vessels, and a needle tip can sit inside one. In a study of 359 lower jaw nerve block injections (Taghavi Zenouz and colleagues, Journal of Dental Research, Dental Clinics, Dental Prospects, 2008), 15.3% drew back blood when checked. That check, called aspiration, shows when the needle tip is inside a vessel. The authors note that anaesthetic with adrenaline reaching a vessel can cause a fast heart rate and a rise in blood pressure.
How much the heart rate usually changes
Several small studies have measured heart rate after dental injections. The largest effects were seen with intraosseous injections, where anaesthetic is placed directly into the bone beside a tooth, sometimes used when a standard injection has not given enough numbness (Brown, Journal of the California Dental Association, 1999).
| Study | Injection | Change in heart rate |
|---|---|---|
| Knoll-Köhler 1989, 12 volunteers | Upper front infiltration, 20 micrograms of adrenaline | About 4 beats a minute higher |
| Knoll-Köhler 1989 | Same injection, 80 micrograms of adrenaline | 5 beats a minute higher from two minutes, reaching 13 beats a minute higher by 15 minutes |
| Chamberlain 2000, 20 volunteers | Intraosseous, lower jaw | 12 beats a minute higher immediately after, no significant change in blood pressure |
| Susi 2008, 61 people | Intraosseous, fast or slow delivery | Average rise of 21 to 28 beats a minute when given fast, 10 to 12 when given slowly |
Wood and colleagues (Journal of Endodontics, 2005) compared an intraosseous injection with an ordinary infiltration in 20 people and found heart rate was higher with the intraosseous injection while the solution was going in and for two minutes afterwards. These were small studies, several of them in healthy young volunteers, so they show the typical size of the effect in those groups rather than what any one person will feel.
True allergy to dental anaesthetic is uncommon
Bhole and colleagues (British Journal of Anaesthesia, 2012) reviewed 23 case series covering 2,978 people investigated for suspected local anaesthetic allergy, and only 29 of them, under 1%, had a confirmed allergic reaction of the immediate type.
Severe allergy (anaphylaxis) tends to show itself differently. Healthdirect lists difficult or noisy breathing, a swollen tongue, swelling or tightness in the throat, difficulty talking or a hoarse voice, wheeze or a persistent cough, and persistent dizziness or collapse among its symptoms. Our article on allergic reactions to dental materials explains how a suspected allergy is investigated.
Fainting is different again. Before a faint, people commonly notice warning signs such as light-headedness, sweating, nausea, or a pale face with cool and moist skin (healthdirect). In a survey of dentists in northern England, fainting was the medical emergency reported most often (Girdler and Smith, Resuscitation, 1999). Our guide to fainting at the dentist covers what to do.
When to get help
If it happens in the chair, tell your dentist straight away, or raise your hand if you cannot speak. Treatment can be paused while you sit or lie back and your breathing and pulse are checked.
After you leave, healthdirect's advice on palpitations applies:
- Call triple zero (000) if you have palpitations along with shortness of breath, chest pain, dizziness or light-headedness, or fainting or blackouts.
- See your doctor urgently if palpitations last more than a few minutes, happen often, or come with a family history of heart rhythm problems.
For general advice at any hour, you can call healthdirect on 1800 022 222.
Heart conditions, blood pressure and medicines
Having a heart or blood pressure condition does not on its own rule out anaesthetic with adrenaline. A systematic review by Godzieba and colleagues (Medical Science Monitor, 2014) found no severe adverse effects in the studies of people with cardiovascular disease. The most common complications were heart rhythm changes seen on ECG, and most of these were not clinically significant. Only 10 complications could be directly linked to local anaesthesia, and 40% of those followed anaesthetic without a vasoconstrictor. The authors concluded that up to four cartridges of a common local anaesthetic with 1:100,000 adrenaline seem to be relatively safe for these patients. An earlier review (Bader and colleagues, Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontics, 2002) found only small, non-significant rises in blood pressure and no adverse outcomes in people with uncontrolled high blood pressure, but noted that the research was limited in amount and quality.
Some medicines matter more. Non-selective beta blockers, a group of heart and blood pressure medicines, can interact with adrenaline and cause a marked rise in blood pressure with a slowing of the heart (Hersh and Giannakopoulos, Dental Clinics of North America, 2010). The interaction appears to be rare in dental care and is usually smaller with one or two cartridges, but it is more pronounced with larger doses or if anaesthetic enters a blood vessel, and some people are more sensitive to it. A group of antidepressants called tricyclic antidepressants can also interact with adrenaline (Yagiela, Journal of the American Dental Association, 1999), which our article on antidepressants and your teeth explains.
Bring a full list of your medicines to every appointment. Never stop or skip a heart or blood pressure medicine before dental treatment on your own. If anything needs to change, your dentist will check with your GP or prescriber first. People planning surgery can read more in our article on implants with a heart condition.
What to say before your next appointment
Tell the team what you felt, how long it lasted and what kind of treatment you were having. That helps your dentist judge whether adrenaline, nerves or something else was the likely cause, and plan the next visit around it. Depending on the treatment, that might mean a different anaesthetic, a smaller amount given more slowly, shorter appointments or extra time to settle before the injection. Anaesthetic without adrenaline exists, although adding adrenaline is one of the ways numbness is made to last longer (Sisk, 1992), which our article on how long dental numbness lasts discusses.
If anxiety is a large part of it, Lumi offers happy gas (relative analgesia), inhaled pain relief, oral sedation and IV sedation, and a free consult for nervous patients. Our page on care for nervous patients explains the options, and our IV sedation page covers what that involves.
Common questions
Does a racing heart after the injection mean I cannot have dental anaesthetic again?
Usually not. True allergy to local anaesthetic is rare, and adrenaline and nerves can both make the heart beat faster, so the next appointment can be planned around what happened. If an allergy is suspected, your dentist may suggest testing with an allergy specialist before more treatment.
How long does the feeling last?
The studies above measured heart rate for 15 minutes or less. Some rises were seen only during or just after the injection, but with the larger dose of adrenaline in one study, heart rate was still at its highest when measuring stopped at 15 minutes. If palpitations last more than a few minutes, or come with chest pain, shortness of breath, dizziness or fainting, follow the healthdirect advice above.
Should I take my usual medicines on the day?
Yes, unless your doctor has told you otherwise. Tell your dentist what you take, and do not stop any medicine on your own.
If you have had a reaction to a dental injection and want to talk it through before your next visit, our team at Lumi Dental in Melrose Park can plan the appointment with you.
Sources
- Knoll-Köhler E, Frie A, Becker J, Ohlendorf D. Changes in plasma epinephrine concentration after dental infiltration anesthesia with different doses of epinephrine. J Dent Res. 1989;68(6):1098-1101. PubMed 2808867
- Sisk AL. Vasoconstrictors in local anesthesia for dentistry. Anesth Prog. 1992;39(6):187-193. PubMed 8250339
- Liau FL, Kok SH, Lee JJ, et al. Cardiovascular influence of dental anxiety during local anesthesia for tooth extraction. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2008;105(1):16-26. PubMed 17656135
- Sharma A, Pant R, Priyadarshi S, et al. Cardiovascular changes due to dental anxiety during local anesthesia injection for extraction. J Maxillofac Oral Surg. 2019;18(1):80-87. PubMed 30728697
- Taghavi Zenouz A, Ebrahimi H, Mahdipour M, et al. The incidence of intravascular needle entrance during inferior alveolar nerve block injection. J Dent Res Dent Clin Dent Prospects. 2008;2(1):38-41. PubMed 23285329
- Brown R. Intraosseous anesthesia: a review. J Calif Dent Assoc. 1999;27(10):785-792. PubMed 10726552
- Chamberlain TM, Davis RD, Murchison DF, et al. Systemic effects of an intraosseous injection of 2% lidocaine with 1:100,000 epinephrine. Gen Dent. 2000;48(3):299-302. PubMed 11199596
- Susi L, Reader A, Nusstein J, et al. Heart rate effects of intraosseous injections using slow and fast rates of anesthetic solution deposition. Anesth Prog. 2008;55(1):9-15. PubMed 18327970
- Wood M, Reader A, Nusstein J, et al. Comparison of intraosseous and infiltration injections for venous lidocaine blood concentrations and heart rate changes after injection of 2% lidocaine with 1:100,000 epinephrine. J Endod. 2005;31(6):435-438. PubMed 15917682
- Bhole MV, Manson AL, Seneviratne SL, Misbah SA. IgE-mediated allergy to local anaesthetics: separating fact from perception: a UK perspective. Br J Anaesth. 2012;108(6):903-911. PubMed 22593127
- Girdler NM, Smith DG. Prevalence of emergency events in British dental practice and emergency management skills of British dentists. Resuscitation. 1999;41(2):159-167. PubMed 10488938
- Godzieba A, Smektała T, Jędrzejewski M, Sporniak-Tutak K. Clinical assessment of the safe use local anaesthesia with vasoconstrictor agents in cardiovascular compromised patients: a systematic review. Med Sci Monit. 2014;20:393-398. PubMed 24608362
- Bader JD, Bonito AJ, Shugars DA. A systematic review of cardiovascular effects of epinephrine on hypertensive dental patients. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2002;93(6):647-653. PubMed 12142870
- Hersh EV, Giannakopoulos H. Beta-adrenergic blocking agents and dental vasoconstrictors. Dent Clin North Am. 2010;54(4):687-696. PubMed 20831932
- Yagiela JA. Adverse drug interactions in dental practice: interactions associated with vasoconstrictors. Part V of a series. J Am Dent Assoc. 1999;130(5):701-709. PubMed 10332135
- healthdirect. Heart palpitations (last reviewed December 2025). healthdirect.gov.au
- healthdirect. Anaphylaxis (last reviewed November 2024). healthdirect.gov.au
- healthdirect. Fainting (last reviewed December 2023). healthdirect.gov.au
This article is general information only and is not a substitute for advice about your own situation from a dentist or doctor.
