Fainting During Dental Injections

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Written by the Dental Fear Central Web Team and reviewed by Dave Carbonell PhD
Last updated on January 17, 2021
Person feeling faint

If you faint at the sight of needles or when you have an injection, you may have what is called a blood-injury-injection (BII) phobia. This page explains what you can do about this.

Some people also faint when they’re extremely anxious or distressed. Here are some general tips:

  1. Eat a meal a few hours beforehand. Admittedly, it can be hard to eat anything when you’re feeling sick with fear. So if you can’t eat at all, make sure you drink something nourishing – for example, a protein shake or a milkshake.
  2. Make sure you drink plenty of water – dehydration makes fainting more likely.
  3. A problem shared is a problem halved. Let your dental team know about your fears – don’t bottle them up!

What causes fainting?

Fainting due to blood-injury-injection phobia is caused by an initial increase in arousal, followed by a sudden drop in blood pressure and heart rate. This type of fainting is called vasovagal syncope. It can also be triggered by extreme emotional distress, straining to have a bowel movement, or heat exposure. Vasovagal syncope is the most common type of fainting.

Some people faint at the sight of needles or blood even they don’t consciously experience any fear whatsoever – it is very much a physiological response, and not everyone who faints during injections is anxious or fearful.

Is fainting dangerous?

People often think of fainting as a physical catastrophe, in the same category as heart attacks. But fainting is actually a self-protective response, not a sign of disease or disaster.

What causes a person to faint? Fainting is caused by a sudden and significant drop in your blood pressure. If your blood pressure drops for whatever reason, the part of your body most likely to get an inadequate supply of blood is your brain, because it’s on the top. The brain, more than any other organ, needs a steady supply of freshly oxygenated blood, and it can be damaged if blood flow is impaired. That’s a problem if your blood pressure drops a lot, and fainting is the body’s response to this problem. If we can’t get enough blood to the brain, fainting brings the brain down to the blood. 1

Psychologists don’t know exactly why some of us experience a significant drop in blood pressure when we see blood or have an injection. One theory is that it’s an evolutionary mechanism. If you see blood, there’s always a chance it’s yours, so a drop in blood pressure is a useful mechanism to ensure you bleed less, and the blood clots faster. Or perhaps, back in the distant past, when someone was coming at someone else with a sharp stick, a genetic variation allowed some individuals to faint in response. Because a person who had fainted looked dead, they might have survived attacks by other warriors during battle. Again, the drop in blood pressure might have helped those who were wounded to avoid bleeding to death. Survivors then passed on the “fainting gene”.

Vasovagal syncope is harmless and requires no treatment. But it’s possible you may injure yourself when you faint, for example by hitting your head (unlikely if you’re sitting in a dental chair at the time!).

If you experience fainting, your GP may want to refer you to a cardiologist to rule out heart problems as the cause.

How can I stop myself from fainting during numbing shots?

The Mayo Clinic website has these tips for preventing vasovagal syncope:

If you feel like you might faint, lie down and lift your legs.

This allows gravity to keep blood flowing to your brain.

You can probably see where this is leading…

What your dentist and you can do:

Fainting – it does happen. I would say a handful of my patients come over faint every year. This tends to happen just after giving local anaesthetic, especially when they have not eaten. Normally, I spot the signs and lay the patient either flat or with their feet slightly raised. I cannot recall the last time a patient actually properly passed out. These days I tend to give local anaesthetic with the patient reclined (if they are ok with that) and keep a close eye on them for the next few minutes.

Lying down helps because the blood can flow to the brain more easily. So if you are concerned about fainting, ask your dentist to give you the local anaesthetic while lying down:

I tend to have vasovagal reactions from dental injections – I actually fainted on one occasion. I realized, after starting to go to my current dentist, that lying flat – or beyond 180 degrees (especially during injections) significantly lessens the vasovagal response. At least I know that, in that position, it is nearly impossible to faint which lessens one of my fears.

What else you can do:

If lying down on its own isn’t enough (or you don’t like the idea of lying down), you can learn a technique called Applied Tension. Ideally, to learn it, you would work with a therapist, because this will make it easier to get ideas for exposure exercises. But you can also learn it on your own. Read through all the instructions first before you start practicing.

Applied Tension Technique

Step 1: Find a comfortable place in your home where you can be alone without anyone interrupting. Sit in a comfy chair or lie down on a sofa or a bed. Focus on the muscles in your legs, arms and trunk. Now tense those muscles (make them contract). Hold the tension until you feel a warm feeling or a “rush” in your head. This usually occurs after 10 to 15 seconds. Then, relax and rest for about 30 seconds. Repeat this four more times.

Step 2: Repeat step 1 five times per day (this means doing it 25 times per day altogether). Do this every day for one week. This may seem like a lot, but the better you get at this technique, the easier it will be when you put it to work in a stressful situation. You want to practice enough that it becomes automatic.

Don’t overdo it, though. If you are getting headaches it could mean that you’re tensing too hard. If this happens, do the tensing exercise less often or don’t tense the muscles as hard.

Step 3: It will be very helpful for you to know the physical symptoms you experience just before you faint. These will be different for different people. You may feel

  • light-headed
  • clammy
  • nauseous
  • hot or cold flushes
  • or other symptoms (everyone is unique!)

If you can recognise the early warning signs, you can then start applied tension to reverse the fainting process and stop the faint before it happens.

Step 4: Now it’s time to practice applied tension while exposing yourself to things that make you feel faint. This exposure starts with “easier” things like looking at a picture of a toy syringe or a drawing of a syringe, for example. As you master each situation, you move on to more difficult things. This is where a psychologist comes in handy because they can help with suggestions for exposure exercises, and with creating an exposure hierarchy. An exposure hierarchy is a list of scenarios that may make you faint (these could be thinking about a situation, looking at a drawing or photo of the feared situation, watching a video, or actually doing it for real), and putting them in order moving from the least scary items to the most.

If you’re not just practicing for dental injections, but for an injection in the arm, you’ll need to relax the arm where the injection will be given while tensing all of the other muscles in your body. This will require some extra practice.

Visit our support forum to get help with this and other fears, or to simply get things off your chest!

Further reading

Sources of Information

  1. David Carbonell. Blood Phobia and Fear of Fainting. https://www.anxietycoach.com/blood-phobia.html (accessed 12 June 2020)[]