11 Silent Signs You Have a Kidney Infection

Head to your doctor for antibiotics if you’re showing these signs that a urinary tract infection has travelled to the kidneys.

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Bloody urine

Most kidney infections will start with bacteria that travel up the urinary tract to the bladder; the infection can then make its way to the kidneys. Because women have a shorter urethra than men, they’re at higher risk for urinary tract infections (UTIs)—and that leaves them more vulnerable to kidney infections. Frequent intercourse or a new partner may also increase a woman’s risk, says Nicole Ali, MD, a nephrologist at NYU Langone. As the body fights the infection, red blood cells can end up in your urine, she says. Don’t miss these other warning signs your kidneys are in big trouble.

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Urge to pee often

That initial bladder infection irritates the organ’s tissues and will probably send you to the bathroom more frequently—it’s one of the earliest kidney infection symptoms says Charles Modlin, MD, MBA, a urologist with Cleveland Clinic. “The bladder senses that irritation and wants to get rid of the irritation, so it contracts,” he says. When it tightens, you’ll feel like you need to pee, even if your bladder is near empty.

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Problems emptying the bladder

In rare cases, problems peeing might be the cause of bladder and kidney infection symptoms rather than the symptom, says Dr. Ali. For men, an enlarged prostate can press against the bladder; for women, it could be the bladder dropping during menopause. Either condition can prevent the bladder from emptying completely; the leftover urine can collect bacteria, which leads to an infection. If you’ve had repeated urinary tract infections—especially men since they’re less likely to get UTIs—talk to your doctor about possible bladder issues.

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Back pain

An infected kidney will swell and be tender; it can press up against the renal capsule that covers the kidneys, says Dr. Modlin. Because your kidneys sit closer to your back than to your belly, that sharp or dull pain would manifest in your lower back, says Dr. Ali. “We’ll give a little bit of a tap to the lower back, and if that hurts, then we suspect the infection has travelled to the kidneys,” she says.

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Pain when peeing

Because a kidney infection is a type of UTI, you’ll have inflammation all the way down your urethra. The bacteria don’t just invade the lining of your bladder and kidneys, explains Dr. Modlin: They’ll infiltrate the tissue and nerve endings of your urinary tract, activating pain receptors in the area. When it’s time to pee—ouch.

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Groin pain

Men might feel the pain of a kidney infection deep in the groin. “When we’re in utero as embryos, our kidneys start lower in our body, and as the fetus grows, the kidneys ascend,” says Dr. Modlin. “They have that same nerve supply as some of the structures down in the groin.” You might think your testicles are the problem, for example, but if you have other UTI symptoms your doctor will test for a kidney infection.

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Cloudy urine

During a kidney infection, your pee might look cloudy. “Your body is sending white blood cells to fight the infection,” says Dr. Ali. “What you see in the urine is blood cells and bacteria building up.”

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Foul smelling pee

Noticing a stench when you urinate could be another one of the kidney infection symptoms you experience. “That’s the fermentation of the bacteria,” says Dr. Modlin. Don’t jump to conclusions if it’s your only symptom, though. Cloudy, strong-smelling urine can also be a sign of dehydration, he says, so see if drinking more water helps.

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Pus in the urine

In severe cases, you might see pus when you pee because of a buildup of white blood cells and bacteria, says Dr. Ali. “At the point where someone is seeing pus in the urine, they probably have a bad infection or abscess in the bladder,” says Dr. Ali.

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An untreated kidney infection can spread to your bloodstream, wreaking havoc on your whole body. “That inflammation from the bacteria is causing your blood vessels to dilate, which makes the blood pressure drop and makes you dizzy,” says Dr. Ali. The shock to your body can be serious and require an IV in a hospital, says Dr. Moldin.

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Bladder infections don’t normally cause a fever, so running a temperature could indicate the infection has traveled up to the kidneys, says Dr. Modlin. As your body ramps up its immune response, your body temperature can climb.

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