Diabetes insipidus is a rare condition where your body can’t properly regulate water balance, causing you to produce enormous volumes of dilute urine and feel constantly thirsty. While most people produce 1 to 3 quarts of urine per day, someone with diabetes insipidus can produce up to 20 quarts. Despite sharing the word “diabetes,” it has nothing to do with blood sugar or insulin. The name simply reflects the shared symptom of excessive urination.
How Your Body Normally Controls Water
Your brain produces a hormone called vasopressin (also known as antidiuretic hormone, or ADH) in a small structure called the hypothalamus, then stores it in the pituitary gland at the base of your brain. When your body senses that you’re getting dehydrated, it releases vasopressin into your bloodstream. The hormone travels to your kidneys and triggers special water channels to open in the walls of your kidney’s collecting ducts, the tubes where urine is being formed. These channels allow water to be reabsorbed back into your bloodstream instead of flowing out as urine. The result is concentrated, darker urine and preserved hydration.
In diabetes insipidus, this system breaks down at one of two points: either the brain doesn’t produce enough vasopressin, or the kidneys don’t respond to it properly. Either way, water passes straight through the kidneys without being reclaimed, producing large amounts of very dilute, almost water-like urine.
The Two Main Types
Central Diabetes Insipidus
Central diabetes insipidus (now formally called “arginine vasopressin deficiency”) happens when the brain fails to produce or release enough vasopressin. The severity depends on how much of the hormone-producing tissue is damaged: partial damage leads to reduced but not absent vasopressin, while complete destruction stops production entirely.
Common causes include head injuries, brain surgery (especially near the pituitary gland), tumors in the hypothalamus or pituitary region, and autoimmune inflammation that destroys vasopressin-producing cells. In some cases, no cause is ever identified. Central DI is the more common of the two main types.
Nephrogenic Diabetes Insipidus
Nephrogenic diabetes insipidus (formally “arginine vasopressin resistance”) occurs when the kidneys can’t respond to vasopressin even though the brain is producing it normally. The receptors on kidney cells that vasopressin is supposed to bind to are either defective or blocked, so the water channels never open.
This type can be inherited through genetic mutations that affect those kidney receptors, though acquired causes are more common in adults. Long-term use of lithium, a medication frequently prescribed for bipolar disorder, is one of the best-known triggers. Chronic kidney disease, high calcium levels in the blood, and certain other medications can also cause it.
Gestational Diabetes Insipidus
A third, less common type occurs during pregnancy. The placenta produces an enzyme called vasopressinase that breaks down vasopressin. This enzyme is present from around the 7th week of pregnancy, but its levels increase roughly 1,000-fold between weeks 7 and 40 as the placenta grows. When the enzyme becomes overly active, it destroys vasopressin faster than the body can replace it. Gestational diabetes insipidus typically appears late in the second trimester or during the third trimester and resolves on its own within 4 to 6 weeks after delivery, once the placenta is gone and the enzyme clears from the body.
What It Feels Like Day to Day
The hallmark symptoms are relentless thirst and frequent, high-volume urination, including throughout the night. People with untreated diabetes insipidus may find themselves drinking and urinating almost constantly. The urine is noticeably pale and watery because the kidneys aren’t concentrating it. Nighttime urination can severely disrupt sleep, leading to fatigue and difficulty concentrating during the day.
In young children and infants, the signs can be harder to spot. Unexplained fussiness, unusually wet diapers, poor weight gain, and a preference for water over milk may be early clues. Bed-wetting in an older child who was previously dry at night can also be a sign.
As long as someone with diabetes insipidus has access to water and can drink freely, they can usually keep up with the fluid loss. The real danger comes when they can’t, whether due to illness, surgery, an altered mental state, or simply not having water available. Without adequate fluid intake, the body loses water rapidly while sodium stays behind, pushing blood sodium levels above the normal threshold of 145 milliequivalents per liter. This condition, called hypernatremia, can cause confusion, seizures, and in severe cases, brain damage.
How It’s Diagnosed
Doctors start by confirming that you’re actually producing an abnormally high volume of urine, generally defined as more than 3 liters per day in adults (or more than 50 milliliters per kilogram of body weight per day). A 24-hour urine collection under 2.5 liters is usually enough to rule out a problem.
The urine itself is tested for concentration. In diabetes insipidus, urine osmolality (a measure of how concentrated the urine is) falls below 300 mOsm/kg, meaning it’s very dilute. A reading above 800 mOsm/kg means the kidneys are concentrating urine normally, which rules out DI. Values between 300 and 800 fall into a gray zone that requires further testing.
The classic next step is a water deprivation test. You stop drinking fluids under medical supervision while your weight, urine concentration, and symptoms are closely monitored. The test continues until you’ve lost more than 3% of your body weight, your urine becomes concentrated enough, or symptoms become intolerable. If your urine stays dilute despite dehydration, it confirms that your body can’t concentrate urine on its own.
To distinguish between the central and nephrogenic types, you’re then given a synthetic version of vasopressin called desmopressin. If your urine concentration jumps up in response, the problem is in the brain (central DI), because the kidneys work fine once they get the hormone they were missing. If the urine stays dilute, the kidneys are the problem (nephrogenic DI), because they’re ignoring the hormone. Newer blood tests measuring a protein called copeptin can also help: very low levels point toward central DI, while elevated levels suggest nephrogenic DI, since the brain is producing vasopressin but the kidneys aren’t using it.
How Diabetes Insipidus Differs From Diabetes Mellitus
The two conditions share almost nothing beyond a name and the symptom of excessive urination. Diabetes mellitus involves problems with insulin and blood sugar regulation. Diabetes insipidus involves problems with vasopressin and water regulation. Blood sugar levels in someone with diabetes insipidus are completely normal. The urine in diabetes mellitus contains glucose (which is why “mellitus” means “honey-sweet” in Latin), while the urine in diabetes insipidus is extremely dilute and essentially tasteless (“insipidus” means “without flavor”). This naming convention dates back centuries, when physicians actually tasted urine to distinguish between the two.
Treatment by Type
Central diabetes insipidus is treated with desmopressin, a synthetic hormone that mimics natural vasopressin but lasts longer in the body. It comes as a tablet, nasal spray, or injection. The tablet form is typically started at a low dose taken twice daily, then adjusted based on how your body responds throughout the day and night. Some people need more coverage overnight to prevent waking up to urinate, while others need more during waking hours. The goal is to reduce urine output to a manageable volume without overcorrecting, since too much desmopressin can cause the body to retain too much water and dilute blood sodium to dangerously low levels.
Nephrogenic diabetes insipidus doesn’t respond to desmopressin because the kidneys can’t use the hormone regardless of how much is available. Treatment focuses on addressing the underlying cause when possible (stopping lithium, for instance, or treating high calcium). Beyond that, a low-salt diet helps reduce urine output, and certain medications that work on the kidney through different pathways can modestly improve water retention. Ensuring consistent access to water is essential.
Gestational diabetes insipidus responds well to desmopressin because the placental enzyme that destroys natural vasopressin does not break down the synthetic version. Treatment continues until the condition resolves after delivery.