What Is Oliguria?

Medically Reviewed by Zilpah Sheikh, MD on December 18, 2023
5 min read

Your kidneys make more or less urine, depending on what your body needs to keep things in balance. If you pee too much or not enough, it can be a sign that something is wrong.

Oliguria is when you pee less than usual. For adults, that means having a decreased urine output of less than 400 milliliters a day. The specific amounts for infants and children are based on their weight (less than 1 milliliter per kilogram per hour for infants, and less than 0.5 milliliters per kilogram per hour for children).

Oliguria vs. anuria

If left untreated, oliguria can lead to a serious condition called anuria. Anuria means your kidneys are producing very little to no pee, at 100 milliliters or 3 ounces of urine or less per day. By comparison, most adults produce around 500 milliliters or 17 ounces of pee per day. Anuria can be caused by conditions that affect your kidneys' ability to filter blood. If left untreated, anuria can be life-threatening.

Lots of different things can cause oliguria. Many of them go away on their own, but some need medical treatment.

Dehydration: This is the most common cause of oliguria. It happens mostly when you've been vomiting or had diarrhea.

Burns and other serious injuries: Burns can dehydrate you and make you pee less. Other kinds of trauma that can cause oliguria include blood loss (hemorrhage), anaphylactic shock from a bad allergy, and septic shock after an infection or surgery.

Obstruction: To get from your kidneys to your urethra -- the tube that takes pee out of your body -- urine has to pass through a maze of “plumbing” called your urinary tract. A blockage anywhere in this area can cause oliguria or even anuria, which is when you don’t pee at all. Many different things can block your urinary tract, such as scar tissue from surgery, kidney stones, or a tumor.

Medicines: Certain drugs can make you pee less, including:

Kidney disease: Oliguria can cause kidney failure, but more often it’s a symptom that your kidneys aren’t working properly.

Diseases of the heart or lungs: Heart failure can increase your risk of oliguria. If your heart can’t pump the right amount of blood to your kidneys, you won’t pee as much as normal. Lung infections can cause fluid buildup in the lungs, which also reduces kidney function and urine production. If you have heart or lung problems, it’s important to get medical treatment for oliguria.

Your doctor will start by asking questions about how long you’ve had the problem, how bad it is, and other things that might be going on with you. For example, they'll want to know if you've been vomiting, had diarrhea, or felt any pain in your belly. You also should tell them about any medications you take.

Your doctor probably will do a physical exam and may want a sample of your pee for testing. Urine tests look for infections or other problems in your urine. In some cases, you may need an imaging test such as an ultrasound so they can get a closer look at your kidneys or other organs. The doctor or urologist also may perform a cystoscopy, where a small camera is used to see inside the bladder.

To prepare for your exam:

  • Keep track of your fluid intake and output over time, if possible.
  • Make a note of whether or not increasing your daily fluid intake increases the amount you pee.
  • Make sure you’ve drunk enough liquid before the appointment, so you’ll be able to produce a urine sample.
  • In most cases, you can eat and drink normally before providing a urine sample. If you’re having an ultrasound, you may be asked to limit food and beverages before the visit.

The treatment for oliguria depends on the cause. If you're dehydrated, your doctor will recommend that you drink more fluids and electrolytes. In serious cases, you may need fluids through an IV (a tube that puts fluid directly into a vein in your hand or arm).

More fluids can also help you pass small kidney stones, as can drugs that relax the muscles in the tube that carries pee from your kidneys to your bladder (the ureter). If the stones are large, your doctor may recommend using sound waves to break them up or surgery to take them out. Surgery can also fix other types of obstructions.

If your doctor decides that your problem is caused by a certain medicine, they may suggest a lower dose or a different medicine. But never stop taking a medication without talking with your doctor first.

If oliguria is caused by kidney disease, you'll see a specialist (called a nephrologist) who will work with you to manage the condition or slow it down. In serious cases, you may need a kidney transplant or dialysis, a process that takes out extra water and toxins from your blood as your kidneys can’t.

One of the most common causes of oliguria is dehydration, which happens when you lose more fluid than you take in. Most of us can prevent dehydration simply by drinking when thirsty. Certain circumstances call for extra precautions:

  • If you're vomiting or have diarrhea, begin drinking fluids at the first sign of illness.
  • Begin hydrating the day before strenuous exercise and remember to drink water during the exercise and afterward.
  • Drink extra water in hot or humid weather and also in cold weather, especially in dry and/or high-altitude conditions.
  • Drink extra fluids when you’re sick or not feeling well, especially if you’re older.
  • If you have kidney, heart, or lung problems, follow your health care provider’s treatment plan carefully to stay hydrated.

Oliguria is when you pee less than usual. It’s commonly caused by dehydration but can become life-threatening if untreated. Certain medications, illnesses, and medical conditions can cause or increase your risk of oliguria. If drinking more fluids doesn’t help, visit your health care provider to determine the cause and best treatment.

What is the main cause of oliguria?

Dehydration is the most common cause of oliguria. It happens most often when you've been vomiting or had diarrhea. It can also be caused by certain medications, medical conditions, or blockages in the urinary tract.