Is it possible to eat to little carbs? I have been low carb for years and I started reducing carbs a little further and got a pounding headache and extreme fatigue. I felt like I had very low blood sugar. This lasted for several weeks and my hair started falling out. I did test my ketones with a blood glucose monitor and I was producing ketones. I finally had to add more carbs to get up and functioning again. Was I eating too little carbs? I was monitoring my protein intake as well.
There is no dietary requirement for carbs. None. Zero.
That said, hair falling out and your other symptoms sound like a thyroid issue. I shouldn’t be armchair diagnosing anything but I would advise you to see an endocrinologist. There are also several nutrient deficiencies that can cause similar symptoms.
Sometimes the mistake people make when they go keto is in not getting a wide enough variety of foods in their diet.
I eat up to 5 grams of net carbs per meal, and usually get that many by eating green leafy vegetables instead of sugary foods like milk, carrots, or other root vegetables. I understand that we need some carbs, aka vegetables, to get micronutrients, including potassium, which is very important in a keto diet.
I agree with AlohaBird about asking a dr. I also wonder if you have been getting enough B vitamins, which can come from carby veggies.
You may have needed more salt. A lot of people have low salt issues when they limit the carbs to the 20 or so recommended for keto. When you go very low carb your body flushes out a lot of salt and it needs to be replaced along with the attached potassium and magnesium. Most find that adding in a good salt like the Celtic Sea Salt and the Redmonds Real Salt will help a lot.