Fasting Side Effect 4: Fainting (syncope)

How It Can Happen

Fainting while fasting can be due to 3 main causes - any three of which should prompt an end to the fast and a thorough medical evaluation.

1. A sudden drop in blood pressure.

The temporary drop in blood pressure associated with suddenly standing from a seated or reclined position is referred to as “orthostatic hypotension. In essence, your body has a set point for its blood pressure- if your blood volume is depleted then its more difficult for your heart to perfuse your brain when you first stand up. This is often sensed as a “head rush” and is a pretty reliable indicator that your volume depleted and in need of hydration. There is a natural reduction in Blood pressure during a fast but for some, this will lower the threshold at which such a “head rush” can occur- and if it drops too low, there is a potential to faint. If this happens, discontinue your fast and consult with a physician before re-engaging in this practice. It may be something simple but that’s for your doctor to figure out. Believing that such a side effect can be overlooked is both dangerous and short-sighted.

2. Your blood glucose dropping below normal.

Your blood glucose should run at least 70 or more at all times. It is possible during a fast that your blood sugar may drop too below that level. At that point, your brain is at risk of not getting the fuel it needs to operate and you may lose consciousness. This is a very dangerous situation- especially for diabetics and is why we do NOT recommend fasting in the setting of diabetes without physician supervision. 3. Volume depletion

This issue is related to issue number one but refers to an overall low blood pressure due to lack of fluid intake overall (not just while standing). In layman’s terms this condition is often thought of as “dehydration” but technically the two terms are somewhat different. IF you are not taking in adequate fluids during your fast, your blood pressure could drop from lack of overall blood plasma volume. The only way for your body to make sure your getting enough blood to your brain is to force you to “lay down”- or faint. As odd as it sounds it's for your own good! Again, make sure a physician checks you out before you simply assume that any fainting spell was due to just not drinking enough water. It’s a simple precaution.

Minimizing the risk of fainting

The truth is that you never know when a fainting episode may or may not occur. However, there are some things you can look for to help you stay in tune with your body so you can anticipate such a problem before it happens.

First off, avoid stress. This is obviously easier said than done but we say it for a reason. Stress releases a cascade of physiologic responses that increase your demand for blood sugar and adequate fluid balance. If you’re getting very hungry, very tired, and/or developing a headache, your blood sugar may be dropping, possibly below normal. When and if you feel these things happening symptoms, it’s wise to NOT operate a motor vehicle. In fact, we advise not driving at all during an extended fast. A fast is supposed to be a time of rest and low stress for a reason!

Maintain good fluid intake and be aware of your surroundings when rising from a seated or reclined position (especially when getting up from the toilet). It's also a good idea to not take a hot water bath or sit in a hot tub for an extended period of time while fasting to avoid episodes of orthostatic hypotension.If you feel like you are going to faint, immediately drop to the floor and elevate your legs above your head for at least 15 minutes. Once you feel you have your bearings, carefully and SLOWLY rise- then seek medical attention.

If you have a fainting episode during a fast, we would recommend breaking your fast (see our Guidelines) at that time. Discuss things with your physician but fainting once doesn't necessarily mean you can’t try it again with supervision. We recommend you discuss with your physician the possibility of getting a glucose monitor and/or a home blood pressure monitor so that you can check your status by taking periodic readings throughout your fast. Not only will this promote safety, you will learn more about your body.