Many factors can affect your urine output.
People with severe kidney problems experience issues with their urine output.
But that does not mean that everyone with a reduced urine output suffers from end-stage renal disease.
There are many factors we should evaluate before considering kidney problems.
First and foremost, we should be aware of what a normal urine output is.
This article will describe normal and abnormal urine output and what causes such variations.
After reading, you will also know how to measure your urine output and what to do if you find abnormalities.
What is a normal urine output?
Urine output is the total amount of urine expelled from the body over a short period. It is a volume measured in milliliters (ml) per hour (ml/h). But it can also be measured in 24 hours and compared with the glomerular filtration rate, which is expressed in milliliters per minute.
All of these measures can help us understand how are the kidneys working.
However, urine output depends on the volume of liquid you drink. People with mild or severe dehydration can have low urine output, even if their kidneys function as they should.
You’ll find another variation depending on your weight. Thus, the technical measure of hourly urine output is 0.5 to 1.5 cc/kg/hour. In other words, the normal urine output range of an individual with 70 kg is 35 to 105 milliliters per hour.
But you could be urinating much more than that, depending on the volume of liquid you’re drinking through the day (1).
So, it depends on your liquid intake, but most people would go to the bathroom at least every 6 hours, which is considered normal.
What is considered low urine output?
As mentioned above, normal urination varies significantly between individuals. Some people produce more than 100 ml of urine per hour, while others experience decreased urination and produce the same amount in around three hours.
The upper threshold level of the normal urine output mentioned above is highly variable. If you drink more than 2 liters a day, you’ll probably visit the toilet more often. So, detecting high urine output is sometimes a bit difficult.
It is not like that with low production of urine. We have a lower threshold set at 0.5 cc/kg/hour, which most health authorities and doctors take as a clear-cut value.
Low urine output is also known as oliguria. The medical definition of oliguria and the diagnosis is made with these values (2):
- Lower than 300cc/m2/24 hours, that’s usually 500 cc/day in adults
- Lower than 0.5 cc/kg/hour in children
- Less than 1.0 cc/kg/hour in infants
Anuria is a more severe condition, which means you’re not producing urine at all or producing an extremely low volume lower than 100 mL/day in adults.
But how do you suspect your urine output is lower than it should be? As mentioned above, most people would go to the toilet at least every 6 hours to urinate.
So, for instance, if you don’t feel the urge to urinate after 9 hours, this fact should alarm you that there’s probably something wrong with your urine output.
In most cases, it is because you’re not drinking enough water and probably experiencing many barriers to water intake.
Some people can forget about drinking water altogether and spend a whole day without consuming more than one or two cups. They may undergo mild dehydration without knowing it, and their urine output reduces in response.
What urine output is too much?
In most cases, you shouldn’t worry about kidney health if you’re producing a higher volume of urine. It is probably related to higher water intake volumes, as mentioned above.
But similar to oliguria, there is something known as polyuria, which means abnormally high urine output. It is measured in your daily urine output and not necessarily by the hour.
Polyuria means producing too much urine, and it is diagnosed when someone produces urine in a volume of:
- 3 liters of urine a day if you’re an adult
- 2 liters per m2 in children
Note that polyuria is not the same as increased urinary frequency, which is commonly seen in benign prostatic hyperplasia and prostate cancer.
Even if you’re using the toilet every hour and waking up to pee every night (nocturia), it doesn’t mean your urine output is increased.
Maybe you have an overactive bladder, or it has reduced the volume it can hold for one reason or another. Thus, you could eliminate one liter of urine like most people but distribute it into more voiding episodes (3).
How can I test my urine output?
Calculating your urine output can be done at home with a very simple test that is also used to measure more complex chemical problems in your kidneys. It is known as a urine 24-hour urine test.
It simply means that you’ll be collecting your urine for 24 hours and then looking at how much urine you’re eliminating.
This test should be performed in a special urine collection container with volume measures, and you can ask for it in any pharmacy. You can also use a urine collection bag.
After buying, wake up the following day and take notes of the volume of water you’re drinking and the time you begin urinating. The next day, try to urinate for the last time at the same hour you started and look at how much volume you’ve got. You can also calculate your urine output per hour by dividing the volume in milliliters by 24.
To get a more accurate urine output calculation, we recommend drinking 2 liters of water throughout the day of the 24-hour volume measure.
Under these conditions, you have oliguria if your urine volume is lower than 500 milliliters. You have anuria if you excrete less than 100 milliliters of urine daily. If the measure is higher than 3 liters, you have polyuria.
Reasons for an abnormal urine output
Now you know what oliguria means, low urine output can have the following causes (2):
- Dehydration: The kidneys work with the fluid in your blood and depend on the volume you drink. Your urine output will naturally decrease when you’re not drinking enough fluids.
- Kidney disease: Most kidney problems can cause a dysfunction of the nephrons. When they no longer work, the glomerular filtration rate and urine output decrease. When the problem is severe, we talk about kidney failure.
- Cardiovascular problems: If you have blood flow problems or congestive heart failure, the kidneys may receive a lower volume of blood and reduce the urine output as organ tissue perfusion reduces.
- Urinary tract obstruction: If the urine flow is obstructed by an anatomical defect or kidney stones (nephrolithiasis), sometimes the urine output becomes blocked, and patients can no longer urinate. This can become a medical emergency.
On the other hand, you can have polyuria in these cases (3):
- Alcohol, caffeine, and diuretics: Alcohol and caffeine are natural diuretics. They increase urine output.
- Diabetes mellitus: Patients with poorly controlled diabetes have excess blood glucose, which increases urine glucose levels. When the urine has too much glucose, it drags more water from the blood, and urine output increases.
How to improve urine output
There are two natural ways to increase the amount of urine your kidneys produce.
Drink more water
The first way to increase your urinary output involves drinking more water. You should drink at least eight glasses of water each day.
Drinking plenty of fluids will help to prevent dehydration. It also allows your kidneys to perform their function more smoothly.
Another thing that you can do to increase the amount of urine that you produce is to exercise. Exercising increases your heart rate and stimulates blood flow to your kidneys. As a result, you’ll end up producing more urine.
In addition to these tips, you may want to try using natural diuretics such as pineapple and green tea.
Some diuretic drugs may also improve your urine output, but they can come with side effects, so you should talk to your doctor to see if they are suitable for you.
How much liquid can a bladder hold?
A human bladder can hold between 300 and 700 milliliters (mL) of fluid. An average person’s bladder can hold around 450 mL of fluid, which is the average for an adult. Women tend to have smaller bladders than men, and they can hold between 400 and 500 mL.
Pregnant women and men with benign prostatic hyperplasia can reduce the volume of urine they can hold.
In both cases, structures outside the bladder put pressure on the organ, reducing its capacity. It is also reduced if you have an overactive bladder or a urinary tract infection.
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What percentage of the water we drink is passed as urine?
When you drink water, it replenishes your fluid losses, which can be up to 800 milliliters a day. After replenishing your fluid loss, the liquid can also be used for metabolic processes, and it could become stuck in the soft tissue in people with fluid retention. But in a healthy body, all the excesses will be used by your kidneys to perform their functions and produce urine.
So, why do you need to drink more than 800 milliliters if your kidneys will eliminate the rest? Because they need a constant flow of liquid to perform their metabolic functions, eliminate toxins, and filter the blood.
Now that you understand normal or abnormal urine output, you can detect some problems and understand what could be the cause.
If you are experiencing any health issues or suspect a problem with your kidneys, make an appointment with your doctor or healthcare provider. They will be able to check your kidney function, order tests if necessary to diagnose the problem, and give you their recommendations.
In the meantime, you can do your part and eat more fruits and vegetables, and don’t forget about drinking enough water.