Ketostix do not measure amounts of ketones they just indicate if they are present in urine or not. The darkness of the strips is usually level of dehydration (darker = more dehydrated). If you want to accurately measure the amount of ketones you need a blood ketone meter. For nutritional ketosis it is recommended by Phinney and Volek, to lose weight, that you achieve a .5 mM or higher level of blood ketones.
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