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HEALTH FAMILY PROBLEMS RELATIONSHIPS EDUCATION & CAREER Dear What's the Problem, For the last three months I have been feeling constantly thirsty. I have to drink lots of water, at least four litres a day and even then I still feel incredibly thirsty and my mouth is always dry. I thought I had diabetes but the glucose level in my blood is OK. In all other aspects my health is good. I eat well and I do a lot of exercise to cope with the stress of my job so I just don't understand why I feel so thirsty all of the time. Is there something seriously wrong with me? Zuo Yan Advice: Dr Mark Hamilton *Well it seems like this has only just started, Zuo Yan said it started three months ago and now he's up to four litres of water a day. Now, it's recommended that on average people should drink about two litres a day and for most people this is actually quite a difficult task, so if he's taking in twice this then I think there is something significant happening. *Zuo Yan mentioned that his blood glucose level is OK so therefore he's not worried about diabetes, but blood glucose levels are an indicator of only one form of the disease. Now you can actually have a different form of diabetes called Diabetes Insipidus and rather than being linked to sugar in the blood it's actually linked to a hormone released from the brain. This hormone controls the rate at which the kidneys filter your blood and therefore produce urine. If the hormone is working properly it stops the kidneys being too porous and letting the blood filter out lots and lots of urine. *But, if this hormone level starts to drop the kidneys will become very porous and will let lots of urine pass through, and consequently you can become very, very thirsty. The What's the Problem? website is providing general information only. It should not be treated as a substitute for the medical advice of your own doctor or any other health care professional. The BBC is not responsible or liable for any diagnosis made by a user based on the content of the What's the Problem? website. Always consult your own GP if you're in any way concerned about your health.		FURTHER INFORMATION   What is diabetes insipidus? Despite a similar name, diabetes insipidus is not related to diabetes mellitus (or sugar diabetes). Some people with diabetes insipidus have kidneys that don't concentrate urine very well (meaning their urine is more diluted). They have to urinate very often. They might wake up 2 or 3 times in the night to urinate. People with diabetes insipidus are thirsty all the time. They often want to drink liquids every hour. What causes diabetes insipidus? In some people, the brain lacks a hormone called ADH, which your body needs to for the kidneys to work effectively. Often, people with diabetes insipidus get it after an injury to the head, after brain surgery, when suffering a brain tumor; it may run in the family, or some medicine, such as lithium, can cause it, although approximately 25% of the time, doctors can't find any reason for it. How do you test for diabetes insipidus? Your doctor will test your urine and blood to check the output of your kidneys and may also give you a brain scan (similar to an x-ray). In mild forms of the disease, when the symptoms are less severe, you may just have to drink more liquid and have regular check-ups from your doctor. When the disease is more serious, a medicine called DDAVP which comes as a nasal spray can help, although this can cause side-effects. If you suspect you may have diabetes insipidus or any other form of the disease, there are many online resources that may help,although it is important that you seek medical advice.    INTERNET LINKS BBC GUIDE TO DIABETES   THE FOUR TYPES OF DIABETES INSIPIDUS   DIABETES INSIPIDUS SYMPTOMS AND ADVICE   The BBC is not responsible for the content of external Internet sites