Normal Urine Output Per Hour

Normal urine output per hour may vary in person-to-person as with many things in life, everyone is different. Therefore, you don’t expect a normal urine output for everybody to be the same.

But medically there is an acceptable number of times an adult should urinate daily. For healthy people, the normal number of times to urinate per day is between 6 – 7 in a 24 hour period. Between 4 and 10 times, a day can also be normal in a healthy person.

In addition, the normal urine output per hour of a person also depends on how much fluid you take in a day. A normal range for an adult urinary output is between 400 to 2,000 milliliters of urine daily. This is also in consideration with a normal fluid intake of about 2 liters per day.

With these expectations and all things being equal, then normal urine output should range between 285.7ml and 500ml per hour.

This Values for normal urinary output varies slightly between laboratories. A urine output of 500 mL per day is generally adequate for normal function. Oliguria urine output is classified as follow: 500 mL in 24 h (Normal output for adult patients: 0.5-1.0 cc/kg/hr) and Normal output for pediatric patients: 1.0-2.0 cc/kg/hr.

Much as well, the types of fluid that you drink matters too. If for example, you are on high blood pressure medication, your urine output may increase. This is because of how some medication works, and a good example of such medicines is “Diuretics”.

More so, how healthy and active you are can influence the urine output. However, age differences may also be a factor too. Take, for instance, the normal frequency of urination in children can be different from that of an adult.

Other factors apart from kidney disease that may influence your hourly or daily urine frequency include water consumption level. Others are the amount of fluid lost in perspiration, your caffeine, and alcohol intake. If your doctor is concerned about your kidneys, a 24-hour urine collection test is typically ordered.

Process of Urine Formation in The Body

The process of urine formation may start from the kidneys. The kidney removes waste products from your blood and expels them in your urine. They accomplish this by filtering your blood.

Your kidneys reabsorb the molecules, nutrients, and water your body needs and excrete concentrated waste products. When the kidneys aren’t functioning properly, waste and fluid that is typically removed from your body in the urine can accumulate and cause disease.

Urine Output and Residual Kidney Function

Very significant residual kidney function in a person may lead to starting dialysis. Such might be with 45 percent, having an estimated glomerular filtration rate (eGFR) greater or equal to 10 mL/min/1.73 m2.

However, preservation of the residual kidney function is seeing as improved outcomes. Hence, nephrologists are expected to preserve this residual kidney function as long as possible.

Even when the GFR is very low, the urine output is variable, ranging from oliguria to normal or even above normal levels. This is in connection with the fact that GFR alone does not determine urine output.

The difference between the GFR and the rate of tubular reabsorption can be a determinant factor. If, for example, someone with advanced acute or chronic kidney failure has a GFR of 5 L/day (versus the normal of 140 to 180 L/day), the daily urine output will still be 1.5 L if only 3.5 L of the filtrate is reabsorbed.

Some medical findings may have it that tubular damage reduces the ability to reabsorb sodium and water. Thereby contributing to the maintenance of adequate urine output in this setting.

However, it seems more likely that volume expansion (due to initial sodium retention) and a urea osmotic diuresis (as the daily urea load is excreted by fewer functioning nephrons), due in part to solute intake, play a more important role in the persistent urine output.

Water intake usually determines the urine output through changes in the secretion of antidiuretic hormone (ADH). This plays relatively little role in regulating the urine output in advanced kidney disease. Patients having kidney problem can neither dilute nor concentrate the urine normally.

The range of urine osmolality that can be achieved in a typical patient with chronic kidney disease varies. It can be from a minimum of 200 mosmol/kg to a maximum of 300 mosmol/kg compared with 50 to 1200 mosmol/kg in a normal situation.

The after effect of this ADH resistance is that variations in ADH release in response to changes in water intake. This may have a considerable effect on the urine output.

Urine output in Diabetes Insipidus Cases

Diabetes insipidus (DI) is a disorder in which polyuria due to decreased collecting tubule water reabsorption is induced. This happens by either decreased secretion of antidiuretic hormone (ADH) or resistance to its renal effects.

In many patients, the level of ADH deficiency or resistance determines the level of polyuria. However, urine output may range from 2 L/day with mild partial DI to over 10 to 15 L/day in patients with severe disease.

There are some basic facts about the determinants of the urine output in patients with DI.

Determinants of Urine Output in Diabetes Insipidus Cases

Determinants of the urine output in non-DI patient and those with DI differs. The urine output in DI patient points at water intake. This leads to alterations in the plasma osmolality that osmoreceptors senses. It is the hypothalamus that regulates both antidiuretic hormone (ADH) release and thirst

In usual cases, an increase in water intake systematically lowers the plasma osmolality. It also decreases ADH secretion and reduces collecting tubule permeability to water. Subsequently, excreting excess water in diluted urine. However, changes in water intake do not result in appropriate changes in urine output in patients with DI.

This can be due to ADH release or that the effect is relatively fixed. Alternatively, urine output is considered constant, regardless of water intake, unless dietary salt and/or protein intake change. If for instance, a patient has moderately severe nephrogenic DI the ADH resistance may not respond to hormone replacement.

The urine osmolality in such patient cannot be above 150 mosmol/kg. Basically, the normal maximum urine osmolality is 900 to 1200 mosmol/kg. In this regard, the excretion of solutes is the major determinant of the urine output.

If the solute excretion is within the usual range of 750 mosmol/kg, the daily urine output will be 5 L/day (750 ÷ 150 = 5). Solute excretion increases urine output per hour, and it reduces with a reduction in solute excretion

In this case, one of the ways to help reduce polyuria is to monitor the level of salt and protein intake. It will also help to reduce the solute load and solute excretion. For example, if solute excretion is at 525 mosmol/day, therefore the urine output would reduce to 3.5 L/day.

On other cases, increasing solute excretion enhances the level of polyuria  This is common in patients with high-protein hyperalimentation. Each gram of protein produces about 170 mg of urea. Therefore, a protein load of 70 g in an adult will generate approximately 11.2 g of urea nitrogen, which corresponds to approximately 400 mmol of urea. At a usual urine osmolality of 300 to 500 mosmol/kg in solute diureses, an increased urea excretion of this magnitude will require a urine output of 0.8 to 1.3 liters.

The Importance Of Measuring Urine Output

Urine output has a lot to show about renal perfusion. More so, a perfused kidney is a happy and healthy kidney performing a normal task. Shock, hypertension, or order health related issues can cause long term damage to the kidney. Especially where there is a serious problem with the blood pressure to the kidney. If such a situation arises, it is necessary to monitor closely if there is any level of decreased urine output.

This can help to alert you of such damage before performing blood-related activities. Urine output can also give you a sign about kidney failure. However, if the output is consistently low or not responding to treatment. This process is a way to evaluate kidney function without checking blood values every four hours.

Monitoring urine output does not have to be an invasive procedure, but it has to be done with a simple technique. While the standard or strict procedure is to place an indwelling urinary catheter connected to a closed collection system. There are many other ways to look at urine and determine different levels of information about your patient.

Firstly, the color of the urine. Usually, brown urine may indicate rhabdomyolysis. This is a dangerous condition from muscle breakdown that can lead to kidney failure. Red or orange urine can mean hemolysis, either from IMHA or from a mismatched blood transfusion. It can also be hematuria from crystalluria or a bleeding disorder.

In case if the blood may not be fresh or hemolyzed, the urine has to be centrifuged. The hemolyzed sample will retain the same color after spinning, blood will centrifuge out leaving a clear supernatant.

Clear or very pale yellow urine may be normal in a person, but can also signify overhydration or an inability of the kidneys to concentrate urine. The doctor or laboratory technician may need to create a list of potential problems just by noting the color of urine.

Monitoring urine concentration can also lead to a clearer understanding of your hydration status. Urine concentration is comparing the weight of urine to distilled water. A specific concentration of 1.000 is dilute, while a concentration greater than 1.040 is concentrated.

Kidneys that are not functioning will be incapable of concentrating urine and will yield a low specific concentration. Monitoring trends in urine specific concentration can help you determine hydration and how well the animal is tolerating fluid therapy.

Lastly, in many patients, it is beneficial to measure the actual output of urine. Not only knowing how many ml/kg/hr produced, but their total input related to their total output.

Identifying A Frequency Problem

If you are concerned about how often you urinate and it is starting to affect your day to day life make an appointment to see your doctor, continence nurse or specialist physiotherapist. A continence nurse and specialist physiotherapist are healthcare professionals who specialize in bladder and bowel problems.

Share this article