Symptoms of Kidney Infection
A kidney infection, also known as pyelonephritis, is a serious medical condition that occurs when bacteria or other pathogens infect one or both kidneys. This type of urinary tract infection (UTI) typically begins in the lower urinary tract, affecting the bladder or urethra, and then ascends to the kidneys. Kidney infections can lead to severe complications if not treated promptly, making it essential to recognize the symptoms early. This article explores the various symptoms of kidney infections, the importance of timely treatment, and the potential complications that can arise.
1. Pain in the Back, Side, or Abdomen
One of the hallmark symptoms of a kidney infection is pain in the back, side, or abdomen. The pain is often described as a dull ache or sharp, stabbing sensation. It usually occurs on one side of the body but can sometimes be felt on both sides if both kidneys are infected. This pain is generally located in the area just below the ribs, often referred to as the flank. The pain may worsen when you move, cough, or press on the area.
In some cases, the pain may be so severe that it can be mistaken for back pain or a muscle strain. However, if the pain is accompanied by other symptoms, such as fever or painful urination, it is more likely to be related to a kidney infection.
2. Fever and Chills
Fever is a common symptom of kidney infections, as the body tries to fight off the infection. The fever typically rises quickly and may be accompanied by chills or shaking. The temperature can become quite high, often exceeding 101°F (38.3°C). In some cases, the fever may be mild, but if it is persistent or worsens, it is important to seek medical attention immediately.

If you experience a fever along with other signs of infection, such as painful urination, back pain, or nausea, you may be dealing with a kidney infection. Untreated fever in this context can lead to more severe symptoms and complications.
3. Painful Urination (Dysuria)
Painful urination, or dysuria, is another common symptom associated with kidney infections. This symptom usually begins in the lower urinary tract, affecting the bladder and urethra, and then spreads to the kidneys. The pain can range from a mild burning sensation to sharp, intense discomfort while urinating. You may also feel a constant urge to urinate, even when your bladder is empty.
If you experience dysuria along with other symptoms such as fever, back pain, and cloudy or foul-smelling urine, it may indicate a kidney infection rather than a simple bladder infection.
4. Frequent Urination
An increased urge to urinate is another symptom that may be seen in people with a kidney infection. The need to urinate more frequently is often associated with bladder infections, but in the case of a kidney infection, it may be accompanied by other, more severe symptoms like fever, flank pain, and nausea.
The frequency of urination can vary, but it is often described as persistent, with little or no urine output. This can be due to inflammation in the urinary tract caused by the infection.
5. Cloudy or Foul-Smelling Urine
Urine may become cloudy, murky, or have a strong, foul odor when you have a kidney infection. This is because the infection can cause changes in the appearance and smell of your urine. The cloudiness may result from the presence of pus, blood, or bacteria in the urine.
In some cases, you may notice that your urine looks reddish or brown, indicating the presence of blood. Hematuria (blood in the urine) is a potential sign of a more serious kidney infection that requires immediate medical intervention.
6. Nausea and Vomiting
Nausea and vomiting are common symptoms of kidney infections, especially when the infection is severe. These symptoms are often caused by the body’s response to the infection, as the immune system releases chemicals to fight the bacteria. The combination of fever, pain, and the body’s response to infection can lead to gastrointestinal upset.
In some cases, nausea and vomiting may be severe enough to prevent you from keeping food or fluids down, which can lead to dehydration. Dehydration, in turn, can worsen kidney function and complicate the infection. If you experience persistent nausea or vomiting, seek medical care immediately.

7. Fatigue and General Malaise
People with kidney infections often experience fatigue and general feelings of being unwell, or malaise. This is a result of the body’s immune system working overtime to fight off the infection. As the body expends energy to combat the bacteria, it can lead to feelings of tiredness, weakness, and a lack of energy.
The fatigue may be accompanied by other systemic symptoms such as body aches and chills. As with other infections, rest and proper hydration are important to support the body’s recovery.
8. Confusion or Altered Mental State (in Severe Cases)
In severe cases of kidney infection, especially in older adults or those with compromised immune systems, confusion or altered mental states may occur. This is a more serious symptom that indicates that the infection has spread or is causing systemic complications. It may be accompanied by other severe symptoms such as low blood pressure or a high fever.
If confusion or delirium occurs in conjunction with the other symptoms of a kidney infection, it is crucial to seek emergency medical attention, as the infection could be progressing toward sepsis, a life-threatening condition.
9. Increased Heart Rate (Tachycardia)
An increased heart rate, or tachycardia, is another symptom that may accompany a kidney infection. As the body fights off the infection, the heart works harder to circulate blood and oxygen to vital organs. This can lead to an elevated heart rate, often above 100 beats per minute.
While tachycardia alone is not necessarily a cause for concern, when combined with other symptoms such as fever, chills, back pain, and nausea, it may indicate a serious infection that requires immediate treatment.
10. Blood in the Urine (Hematuria)
Haematuria, or blood in the urine, is a more alarming symptom of a kidney infection. While blood in the urine can occur with lower UTIs or bladder infections, its presence in a kidney infection can signal more severe inflammation or damage to the kidney. The urine may appear pink, red, or brown due to the presence of blood.
Hematuria is typically accompanied by other symptoms of infection, including fever, pain, and changes in urination habits. If you notice blood in your urine, it is important to seek medical care promptly.

11. Complications of Kidney Infections
If left untreated, kidney infections can lead to serious complications, including:
- Chronic Kidney Disease (CKD): Recurrent kidney infections can damage the kidneys over time, leading to chronic kidney disease, which can affect kidney function and overall health.
- Sepsis: A kidney infection can spread to the bloodstream, causing sepsis, a life-threatening condition characterized by widespread inflammation, organ failure, and shock.
- Kidney Abscess: In some cases, an untreated kidney infection can result in the formation of a kidney abscess, a collection of pus within the kidney that requires surgical drainage.
- Scarring of the Kidneys: Repeated kidney infections can cause scarring of the kidney tissue, which may impair kidney function and increase the risk of future infections.
12. When to See a Doctor
If you experience any combination of the symptoms described above, it is crucial to see a doctor as soon as possible. Early diagnosis and treatment are essential to prevent complications and ensure a full recovery. Kidney infections are typically treated with antibiotics, and in severe cases, hospitalization may be required.
Conclusion
Recognizing the symptoms of a kidney infection is vital to preventing severe complications. From pain in the back or side to fever, nausea, and changes in urination, the signs of a kidney infection should not be ignored. Prompt medical attention can help reduce the risk of long-term damage to the kidneys and ensure a full recovery. If you suspect you may have a kidney infection, it is always best to consult a healthcare provider who can conduct tests and provide the appropriate treatment to address the infection.
What are the common symptoms of a kidney infection?
Common symptoms include lower back pain, fever, chills, nausea, vomiting, painful urination, frequent urination, and cloudy or foul-smelling urine.
How can I treat kidney infection symptoms at home?
Kidney infections require medical treatment, typically antibiotics. It’s essential to see a doctor if you suspect you have a kidney infection for proper care.
Can a kidney infection cause fever?
Yes, fever is a common symptom of a kidney infection, often accompanied by chills and sweating as the body tries to fight the infection.
What should I do if I suspect a kidney infection? I
f you experience symptoms such as fever, pain, or changes in urination, seek medical attention immediately to receive the correct diagnosis and treatment.
How do I know if I have a kidney infection?
If you experience symptoms like persistent back pain, fever, and painful urination, it's important to consult a healthcare professional for diagnosis and treatment.