Sofie Wise

Anjali Dixit

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About Author — Dr. Anjali attended Stanford University and is continuing her training in anesthesiology at UCSF. She has a background in public health and an interest in how technologies can shape U.S. healthcare.

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Fainting is pretty uncommon and it can be quite scary when it happens. People might worry that they will faint again, which could be especially dangerous if they are driving or if they live alone. If you have fainted or lost consciousness recently, it would be wise to consult a doctor to figure out what’s going on. Identifying the cause of your fainting will help you minimize the risk of fainting in the future. Here are a few possible causes of fainting that a doctor might consider:

• Dehydration: This is probably the most common cause of fainting. If you don’t have enough volume of blood and other fluid in your circulation, your brain won’t get enough oxygen. The body compensates for this by causing a person to faint (and fall to the ground) – which makes it easier for blood to get to the brain since it doesn’t have to fight gravity! This is why people usually “come to” once they’ve been supine down for a few moments. Of course, it’s still important to treat the cause of their dehydration. A doctor might ask you if you’ve lost fluid by sweating a lot (through extreme exercise or on a really hot day), if you’ve had any recent bleeding  (e.g., through menstruation), andor if you’ve had any recent diarrhea or vomiting. He or she might also check your heart rate, blood pressure, temperature, and/or order a few blood tests. This will help determine how best to treat your dehydration.

• Vasovagal: “Vasovagal syncope” is a fancy medical way of saying that a person had a change in their body that caused them to faint. The change is not caused by a disease or disorder – instead, it happens because of an extreme feeling like shock, fear, or pain. It also happens in certain other situations (e.g., seeing blood, urinating). People with vasovagal syncope often describe sweating, feeling dizzy or nauseous, or having clammy hands or skin before they faint. They will usually regain consciousness after lying flat for a few minutes. A doctor will ask you about the situation surrounding your loss of consciousness to identify vasovagal syncope. Treatment usually involves avoiding the type of situation that caused the fainting spell – if this is not possible, there are other behavioral and medical treatments that a doctor could prescribe for you.

• Cardiogenic: “Cardiogenic syncope” is another fancy medical term that means that the cause of the fainting spell is due to an issue with the heart. If the heart pumps erratically or inefficiently, enough blood will not get to the brain. This can cause a person to faint so that the blood circulation doesn’t have to fight gravity to get to the brain tissue. Patients with cardiogenic syncope usually don’t have any symptoms before they faint – they often describe feeling totally normal and then just losing consciousness. In this case, a doctor might order an electrocardiogram (EKG), which is a non-invasive way of seeing how the heart is beating. He or she might also order a few other tests to check how your heart is functioning. There are lots of different treatments for cardiogenic syncope – a doctor would be able to discuss these with you after identifying the exact disorder in the heart.

• Seizure: All seizures don’t look like what is portrayed in the movies or on TV – sometimes people having seizures don’t have any twitching movements but they might have other abnormal or uncontrollable symptoms and lose consciousness. A doctor will take a careful history from you to see whether seizure is something he or she should consider. Seizures can be caused by medications, by imbalances in the electrolytes in your body, or by structural changes in your brain – so if your doctor suspects that you may have had a seizure, he or she would order tests such as an EEG to figure out what might be causing the seizure. Treatments would be chosen after identifying the root cause.

These are a few of the major causes of fainting, though there are many others that a doctor would consider as well. If you’ve experienced a fainting episode, we recommend speaking with a doctor about it.

As always, PlushCare doctors are available for consultation about your health. Our doctors can evaluate you and help determine what the best tests and/or treatments might be.

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