Wiktionary(1.00 / 1 vote)Rate this definition: quantity(Noun) A fundamental, generic term used when referring to the measurement (count, amount) of a scalar, vector, number of items or to some other way of denominating the value of a collection or group of items. You have to choose between quantity and quality.
When the body is making and using ketones we say that the body is in a state of ketosis. Ketosis begins after about 48 hours (2 days) or water fast for women, or about 72 hours (3 days) of water fast for men.
I have been doing a ketgenic diet (565 days+) with all days having a blood ketone fasting level over 0.5 or greater with the average around 1.8. Over time the levels are reducing while fasting glucose is rising. I still test my fasting blood ketone as over 0.5 but it tends to range in the 0.8 to 1.3 range.