Fiducia TogetherDiabetes insipidus
Also called Arginine vasopressin deficiency, Water diabetes
Nothing to do with sugar diabetes. Passing enormous volumes of urine, and missing a dose of the treatment in hospital has killed people.
Important: This page is general information, not medical advice, and it is not a diagnosis. If you are worried about your health or someone else's, speak to a GP, pharmacist, or call 111. In an emergency, call 999.
What it is
A condition in which the body cannot concentrate urine, so huge volumes of dilute urine are passed and the person is constantly thirsty.
It has nothing to do with type 1 or type 2 diabetes, and the shared name has caused enough confusion and harm that the condition is being renamed: the central form is now called arginine vasopressin deficiency, and the kidney form arginine vasopressin resistance.
The central form results from lack of the hormone vasopressin, usually after pituitary surgery, head injury, a tumour or inflammation. The kidney form is a failure to respond to it, from lithium, high calcium, or an inherited cause.
Volumes are striking: three to twenty litres a day, with constant thirst and getting up repeatedly at night.
**The safety issue that matters most is missed desmopressin in hospital.** People admitted for something unrelated have died because their desmopressin was not given, or because they could not access water. This has been the subject of national patient safety alerts. Anybody with this condition should carry an alert card, and any admission should flag it immediately.
Treatment of the central form is desmopressin, and of the kidney form is treating the cause plus specific measures.
A person who is drinking large volumes should never be fluid-restricted without specialist advice.
Signs you might notice
Passing very large volumes of pale, dilute urine, day and night.
Extreme thirst, and a strong preference for cold water.
Getting up repeatedly at night to pass urine.
In children: bedwetting after being dry, poor growth, irritability, fever, and unexplained dehydration.
Tiredness and difficulty concentrating from disturbed sleep.
Urgent: rapid dehydration, confusion or drowsiness, particularly if the person cannot drink freely.
**Any hospital admission is a risk point.** Ensure desmopressin is prescribed and given, and that water is accessible.
Distinguish from type 2 diabetes, where thirst and passing urine are also features but the urine contains sugar and a finger-prick test is abnormal.
How it can affect day-to-day life
Access to water and a toilet governs daily life: work, travel, meetings, exams and long journeys all have to be planned around it.
Desmopressin needs careful dosing. Too much causes water retention and dangerously low sodium, with headache, nausea, confusion and seizures, so a planned break to allow a period of urination is often part of the regimen.
For anybody who cannot express thirst or reach a drink independently, a child, someone with a learning disability or dementia, this condition is dangerous, and free access to fluid must be written into the care plan.
Lithium is a common cause of the kidney form, and kidney function and urine volumes should be monitored in anybody taking it long term.
Alert cards, hospital passports and a clear note at the front of the record are the practical protections.
Supporting someone well
Carry an alert card and make sure any hospital admission flags the condition immediately.
Never allow desmopressin to be omitted in hospital, and question it if the dose is late.
Ensure free access to water at all times; never fluid-restrict without specialist advice.
Watch for the opposite problem: headache, nausea, confusion or seizures from too much desmopressin and low sodium.
For anyone dependent on others for drinks, write free access to fluids into the care plan explicitly.
Monitor kidney function and urine output in anybody on long-term lithium.
Get sudden increases in thirst and urine volume assessed rather than assumed.
Keep endocrinology follow-up.
Where to get help
A GP practice for referral to endocrinology; a specialist pituitary centre for the central form.
The hospital team immediately on any admission, to ensure desmopressin is prescribed.
999 for confusion, drowsiness or seizures.
Pituitary Foundation run a helpline and provide alert cards.
Tools we make that might help
These are our own products. We have put them here because they do something specific for this condition, not because every page needs a list.
Fiducia Guardian
Free access to fluids and desmopressin timing recorded as care tasks, because both are things that get missed when somebody else is in charge of the day.
Last reviewed 2026-08-28 by Fiducia Together · Next review due 2027-08-28
Important: This page is general information, not medical advice, and it is not a diagnosis. If you are worried about your health or someone else's, speak to a GP, pharmacist, or call 111. In an emergency, call 999.