Dehydration affects the kidneys by forcing them to retain water. Severe dehydration can reduce kidney function and lead to acute kidney injury (AKI).

Dehydration is a common cause of hospital admission. Not only can it be fatal, but it can also worsen many health conditions. Dehydration affects the kidneys in many ways. For example, it can increase the risk of kidney stones and urinary tract infections (UTIs).

This article explores how dehydration affects the kidneys, the potential causes of dehydration, and the effects of fluid intake on kidney failure. It also discusses some tips for maintaining kidney health.

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People are continuously losing water through their skin, lungs, kidneys, and gastrointestinal (GI) tract. When the loss of water is higher than the gain, receptors in the brain begin to detect a lack of water in the blood and release antidiuretic hormone. This prompts the kidneys to reabsorb more water.

As blood pressure decreases, this triggers the kidneys to release renin, which is an enzyme. Renin converts a hormone called angiotensin 1 to angiotensin 2. As the level of angiotensin 2 increases, the adrenal glands release aldosterone, another hormone. Aldosterone further increases the reabsorption of water and sodium in the kidneys.

Dehydration can play a role in the development of UTIs and kidney stones.

When a person is severely dehydrated, they may develop AKI, which is when the kidneys can suddenly decline in function. This means that waste products can build up in the blood as the kidneys are not filtering them out of the body as effectively as usual.

AKI does not always cause symptoms, but some signs of the condition include:

A person needs to seek medical attention if they think they may be experiencing AKI.

Older adults, in particular, are more likely to experience dehydration because they often have underlying health conditions. Some examples include diabetes, kidney disease, and problems with mobility.

People with access to water rarely become severely dehydrated. Instead, dehydration is usually a complication of an illness. For example, a person with diabetes may experience dehydration when their blood sugar levels are very high.

Severe dehydration reduces kidney function, and causes include:

A person needs to speak with a healthcare professional about how to treat and manage any underlying health conditions to help prevent dehydration.

There are two types of kidney failure: AKI and chronic kidney disease. AKI refers to a sudden loss of kidney function, while kidney failure due to chronic kidney disease results from a gradual loss of kidney function.

Healthcare professionals may advise that individuals with kidney failure from chronic kidney disease reduce their fluid intake. Before making any changes to their fluid intake, a person needs to discuss this with their doctor.

If a doctor thinks a person is experiencing AKI, they may recommend the person undergo a fluid challenge. The purpose of the fluid challenge is to monitor fluid intake and urine output.

If a person’s kidneys improve when they drink more fluid, they likely have prerenal AKI, which tends to occur when there is reduced blood flow to the kidney. This can occur in any individual.

When a person retains fluid during the challenge or experiences fluid overload, they will likely need diuretics, and a doctor will need to monitor their potassium, phosphorus, and sodium intake. However, diuretics may worsen AKI in some cases.

There are plenty of ways a person can help maintain optimal kidney health, including:

  • keeping blood pressure below 140/90 millimeters of mercury or the target the doctor has set
  • staying in a healthy blood sugar range
  • getting or staying physically active
  • engaging in a kidney-friendly diet, which may involve eating more fruits and vegetables and less salt
  • taking any medications as a doctor instructs
  • quitting smoking, if applicable

When a person has severe dehydration, it can contribute to acute kidney injury (AKI), which is a type of kidney failure.

Dehydration increases the amount of metabolic waste in the body, as the kidneys can no longer flush this waste out as well as they used to. Furthermore, the more dehydrated a person is, the more the brain stimulates the kidneys to retain more water and sodium.

Eventually, this breakdown in processes can cause AKI. When this happens, the kidney cannot properly filter out waste from the blood, which can be fatal if a person does not receive prompt treatment.

Because people are always losing water through their skin and other organs, they need to ensure they stay hydrated. However, those with kidney failure due to chronic kidney disease may need to limit their fluid intake, depending on a doctor’s guidance.