hi Karen, and welcome to our forum.

Hypoglycemia (too low blood sugar) results from having too much insulin ... and you get too much insulin from eating a big dose of sweets or processed white flour, white bread, white rice etc. If you didn't eat any carbs, then a possible explanation is not enough PROTEIN. When you cut out the carbs, you need to eat more protein ... have smaller meals more frequently during the day. And especially important to have protein at breakfast. Keeping a steady supply of protein will keep the blood sugar level steady. It's the sudden drops which cause the problems, and insulin is the only thing that will cause a sudden drop.

Are you drinking lots and lots of water??? Being dehydrated can make your blood pressure very low ... especially since low-carbing and ketosis will make you lose a lot of water in the urine. You must drink at least 64 fl. oz per day, plus 8 additional oz for every 25 lbs you need to lose.

Low potassium levels can cause faintness and weakness. Potassium will be lost in the increased urine as well .. you need to replace it with supplements or by using a salt-substitute product such as NoSalt or NuSalt. But make sure you are well-hydrated first, before adding potassium

I'm sorry you had such an unpleasant experience, and hope you're feeling better now.

Doreen