Yep. Will look and see why, hang on.
Couldn't find the appropriate answer so this is taken from a low-carb diet FAQ...
Frequent Urination: After the first day or so, you'll notice that you are in the bathroom urinating more often. Your body is burning up the extra glycogen (stored glucose) in your liver and muscles. Breaking down glycogen releases a lot of water. As your carb intake and glycogen stores drop, your kidneys will start dumping the excess water.
In addition, as your circulating insulin levels drop, your kidneys start excreting excess sodium, which will also cause more frequent urination. (see this reference).
Fatigue and Dizziness: As you start dumping water, you'll lose minerals such as salt, potassium and magnesium as well. Having lower levels of these minerals will make you very, very tired, lightheaded or dizzy, give you muscle cramps, and headaches. This is one of the most common of the low carb diet side effects, and it can be avoided for the most part by making sure you get enough replacement minerals.
You can counteract the mineral losses by eating more salt or drinking salty broth, and eating potassium containing foods. (Dairy foods, green leafy vegetables and avocados are high in potassium).