The kidneys are vital organs with multiple functions, including:
- Balancing the body’s fluids and electrolytes
- Removing waste products from the blood
- Releasing hormones that regulate blood pressure
- Helping production of red blood cells
- Promoting strong bones

When the kidneys are unable to function properly, the body may retain excess fluid and toxins, and electrolytes may be imbalanced. Other consequences of renal insufficiency include high blood pressure, anemia, and weakened bones.

Acute kidney injury (AKI) is a temporary condition which may be caused by impaired blood flow to the kidneys, direct damage to the kidneys, dehydration, blood loss, or certain medications. Chronic kidney disease (CKD) develops over time, in stages, and is usually the result of another long-term condition, such as hypertension or diabetes mellitus. Individuals with CKD are at increased risk for AKI, a condition termed acute on chronic renal failure (ACRF), and cardiovascular disease.

Kidney disease is diagnosed with urine and blood testing. Protein in the urine, albuminuria, may indicate kidneys are not filtering the blood adequately. Elevated creatinine (Cr) in the blood also occurs with impaired blood filtration and is used to calculate glomerular filtration rate (GFR), which determines the stage of kidney disease.

Both AKI and early CKD often occur without symptoms, therefore at-risk individuals benefit from routine blood work. In severe or late stage illness, patients may experience any or all of the following symptoms:
- Fatigue
- Confusion or difficulty concentrating
- Dry, itchy skin
- Fluid retention, particularly in the lower extremities
- Puffiness around the eyes, especially in the morning
- Decreased urine output or excessive urination, more commonly at night
- Poor appetite
- Nausea
- Insomnia
- Weakness
- Shortness of breath
- Muscle cramps
- Irregular heartbeat
- Chest pain or pressure
- Seizures

AKI is often resolved with intravenous fluid, adjustment of medications, or temporary dialysis, and infrequently requires dietary modifications. Although not a cure, a proper diet can help slow the progression of CKD. Nutritional recommendations vary from person to person and are largely dependent on lab results and the amount of weight variation from day to day. Special attention is given to sodium, potassium, phosphorus, fluid, and protein. In stages one through four of chronic kidney disease, protein is restricted. Once a person is on dialysis, protein needs are significantly increased due to losses in the dialysate. The other aforementioned nutrients are usually restricted in all stages of kidney disease as elevated levels resulting from poor blood filtration can cause additional health problems.

Dietary guidelines for kidney disease are often confusing as some of the most nutritious foods are prohibited, therefore registered dietitians are instrumental in educating individuals with renal disease and helping them with meal planning. Proper nutrition is essential for weight maintenance, slowing the progression of disease, and preventing further health complications.