How long is too long?

I’m 33 hours in to a 72 hour fast. I’ve been doing intermittent fasting for a few months now (generally 18-20 hours). This isn’t my first extended fast - the longest was 84 hours, but the hunger pangs are not going away at all this time, and I have a mild headache too. I feel cold and my toes are slightly tingly (winter effect? Low blood sugar? I’m very confused). Should I keep going since I don’t feel weak or dizzy. How do I know if I’ve fasted too long?

Answer

I had two tingling toes on my right foot the 3rd day of a water fast during a cold spell recently. Feel like electrolytes and cold contributed to it, but I ended my fast after 4 days because of low blood sugar. So, a major component is definitely low blood sugar but your body’s starting to use ketones (fat) for fuel too. So, nothing much to worry about if you carry on the fast with sufficient electrolytes. I’m starting a 5-day fast tomorrow, and supplementing electrolytes from the start.