Weight is a good guideline for blood volume in people of average build. This is why we set a minimum weight limit of 7st 12lbs (50 kg) because if more than 13% of blood volume is taken there is more risk of the donor feeling faint after donating.
Not surprisingly, the one factlet most often offered up as revealed truth is wholly false: Your hair and nails do not continue to grow after you die; it's all optical illusion. The sorry fact of the matter is that we dehydrate after dying. Our flesh dries and, in so doing, pulls away from nails and hair.
Once you stop chemo treatment the hair will grow back in. I lost my hair 10 days after my first treatment for breast cancer but I think it can vary on the types of treatment/cocktail of drugs. I didn't lose my eyelashes or eyebrows until I started radiation long after my chemo treatments.