wee on the stick, wait 15 seconds and then read the colour of the stick against the bottle . It will either be a beige colour which is negative , or various shades of pink , which is postive . If it is positive , matter what shade of pink , you are in ketosis
Actually, you might not be dehydrated. If the stick goes deep purple, it means that there are a lot of ketones in the urine specimen. It might mean that you're dehydrated. If you tested first thing in the morning without having a drink first, dehydration is a likely culprit - but then you generally are dehydrated first thing in the morning.
However, if it's a sample from later in the day, and you're sure you've had lots to drink, it might just be that in burning fat, you've produced a lot of ketones. Some people do - and because there are more ketones than the body needs for energy, they spill over into your urine. Some people's bodies are very efficient with ketones - they make just enough to use with minimal spillage into the urine - which means nothing will show up on the ketostick. Yes, you can be in ketosis without the stick ever going pink, folks (one of the reasons I've never bothered with them - I know I'm in ketosis because of how my mouth tastes (yuck) and because I'm aware of feeling a rather odd buzz...)
You'll produce a lot of ketones if you've just exercised as well - cos you'll have broken down fat. Similarly, you might produce lots of ketones if you've just gorged yourself silly on cheese - cos ketostix aren't clever enough to tell the difference between breaking down body fat reserves and breaking down fatty food intake.
So if you're sure you've drunk enough, don't worry too much.