Medical Conditions

Hemolytic Uremic Syndrome (HUS) in Children

Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist

Content reviewed against published AAP, NIDDK, CDC guidelines

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If your baby has been diagnosed with or you suspect hemolytic uremic syndrome (hus) in children, here is what the evidence says.

The short answer

Hemolytic uremic syndrome (HUS) is a serious condition characterized by a triad of hemolytic anemia (destruction of red blood cells), thrombocytopenia (low platelets), and acute kidney injury. It most commonly follows bloody diarrhea caused by E. coli O157:H7 infection. HUS is a medical emergency requiring hospitalization. With supportive care, most children recover kidney function, but early recognition and treatment are critical.

Key takeaways

  • Hemolytic uremic syndrome (HUS) is a serious condition characterized by a triad of hemolytic anemia (destruction of red blood cells), thrombocytopenia (low platelets), and acute kidney injury. It most commonly follows bloody diarrhea caused by E. coli O157:H7 infection. HUS is a medical emergency requiring hospitalization. With supportive care, most children recover kidney function, but early recognition and treatment are critical.
  • Usually normal when: Your child has a mild stomach bug with non-bloody diarrhea and is maintaining good urine output and hydration
  • Call your doctor if: Your child becomes pale, lethargic, or very irritable several days after the onset of bloody diarrhea, as these are warning signs of developing HUS
  • Varies by age — see the age-by-age breakdown below
“Fever itself is not an illness — rather, it is a sign or symptom that the body is fighting an infection. Fever stimulates certain defenses, such as the white blood cells, which attack and destroy invading bacteria.”
— Fever and Your Child, American Academy of Pediatrics (AAP)

Parents everywhere have the same worry. You are doing the right thing by looking into it.

What Parents Should Know

According to AAP, NIDDK, CDC guidelines, hemolytic uremic syndrome (HUS) is a serious condition characterized by a triad of hemolytic anemia (destruction of red blood cells), thrombocytopenia (low platelets), and acute kidney injury. It most commonly follows bloody diarrhea caused by E. coli O157:H7 infection. HUS is a medical emergency requiring hospitalization. With supportive care, most children recover kidney function, but early recognition and treatment are critical. At 0-6 months, hUS is very rare in young infants. Breastfed babies are generally protected from the foodborne E. coli infections that trigger typical HUS. However, atypical HUS (not caused by E. coli) can occur at any age due to genetic mutations in complement regulation. Any infant with unexplained pallor, decreased urine output, or petechiae (tiny red spots on the skin) needs prompt medical evaluation. It is generally considered normal when your child has a mild stomach bug with non-bloody diarrhea and is maintaining good urine output and hydration. However, you should contact your pediatrician promptly if your child becomes pale, lethargic, or very irritable several days after the onset of bloody diarrhea, as these are warning signs of developing HUS.

Sources: [1], [2], [3]

Normal vs. Concerning

Usually Normal
Worth Discussing
Your child has a mild stomach bug with non-bloody diarrhea and is maintaining good urine output and hydration
Your child becomes pale, lethargic, or very irritable several days after the onset of bloody diarrhea, as these are warning signs of developing HUS
Your child had brief diarrhea that is resolving and they are returning to normal activity and eating
Your child has significantly decreased urine output or has not urinated in 8-12 hours, especially following a diarrheal illness
Your child looks well, is not pale, and has normal energy levels during or after a GI illness
Your child develops unexplained bruising, petechiae (tiny red dots on the skin), or appears yellow (jaundiced) after a GI illness
Your child has occasional loose stools without blood and is drinking fluids well
Your child with known or suspected HUS becomes increasingly drowsy, confused, or has seizures, which may indicate severe kidney failure or brain involvement

When to Seek Immediate Care

  • Your child becomes pale, lethargic, or very irritable several days after the onset of bloody diarrhea, as these are warning signs of developing HUS
  • Your child has significantly decreased urine output or has not urinated in 8-12 hours, especially following a diarrheal illness
  • Your child develops unexplained bruising, petechiae (tiny red dots on the skin), or appears yellow (jaundiced) after a GI illness
  • Your child with known or suspected HUS becomes increasingly drowsy, confused, or has seizures, which may indicate severe kidney failure or brain involvement

By Age

What to expect by age

0-6 months

HUS is very rare in young infants. Breastfed babies are generally protected from the foodborne E. coli infections that trigger typical HUS. However, atypical HUS (not caused by E. coli) can occur at any age due to genetic mutations in complement regulation. Any infant with unexplained pallor, decreased urine output, or petechiae (tiny red spots on the skin) needs prompt medical evaluation.

6 months - 3 years

This is the most common age group for typical (Shiga toxin-associated) HUS. It usually begins 5-10 days after the onset of bloody diarrhea from contaminated food or water. Warning signs that HUS is developing include pallor (the child looks washed out), decreased urine output, lethargy, and irritability even as the diarrhea may be improving. Small bruises or pinpoint red spots on the skin indicate low platelets. Do not give antibiotics or anti-diarrheal medications for suspected E. coli diarrhea, as these may increase the risk of HUS.

3-8 years

Children in this age group remain at risk for HUS following E. coli O157:H7 infection, particularly from undercooked ground beef, unpasteurized milk or juice, contaminated water, or contact with farm animals. About 5-15% of children with E. coli O157:H7 infection develop HUS. Parents should watch for a child who becomes increasingly pale, tired, and produces less urine in the days following a bout of bloody diarrhea. Blood work will show anemia, low platelets, and rising kidney markers.

8 years+

While HUS can occur at any age, it is less common in older children. Older children may be better able to describe symptoms such as feeling very tired, having dark or reduced urine, or noticing bruises. Any child recovering from a diarrheal illness who develops these symptoms should be evaluated urgently. Atypical HUS (complement-mediated) should be considered in any child with HUS features without a preceding diarrheal illness.

What to Tell Your Pediatrician

  • Describe when you first noticed hemolytic uremic syndrome (hus) in children and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your child has bloody diarrhea, even if they seem well otherwise, as E. coli O157:H7 should be considered and a stool culture obtained.
  • Mention if your child seems more tired than expected during recovery from a stomach illness.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

What Should You Do?

When to take action

Probably normal when...
  • Your child has a mild stomach bug with non-bloody diarrhea and is maintaining good urine output and hydration
  • Your child had brief diarrhea that is resolving and they are returning to normal activity and eating
  • Your child looks well, is not pale, and has normal energy levels during or after a GI illness
  • Your child has occasional loose stools without blood and is drinking fluids well
Mention at your next visit when...
  • Your child has bloody diarrhea, even if they seem well otherwise, as E. coli O157:H7 should be considered and a stool culture obtained
  • Your child seems more tired than expected during recovery from a stomach illness
  • You notice that your child is urinating less frequently than usual during a diarrheal illness
  • Your child looks paler than normal after a recent gastrointestinal illness
Act now when...
  • Your child becomes pale, lethargic, or very irritable several days after the onset of bloody diarrhea, as these are warning signs of developing HUS
  • Your child has significantly decreased urine output or has not urinated in 8-12 hours, especially following a diarrheal illness
  • Your child develops unexplained bruising, petechiae (tiny red dots on the skin), or appears yellow (jaundiced) after a GI illness
  • Your child with known or suspected HUS becomes increasingly drowsy, confused, or has seizures, which may indicate severe kidney failure or brain involvement

What You Can Do at Home

  • Keep track of when you notice hemolytic uremic syndrome (hus) in children — noting the time of day, duration, and any triggers can help your pediatrician.
  • Remember that your child has a mild stomach bug with non-bloody diarrhea and is maintaining good urine output and hydration — this is generally within the range of normal.
  • At 0-6 months, focus on observation rather than intervention unless your pediatrician advises otherwise.
  • Follow any care instructions from your pediatrician. Keep a written log of symptoms to bring to appointments.
  • While monitoring at home, seek immediate care if your child becomes pale, lethargic, or very irritable several days after the onset of bloody diarrhea, as these are warning signs of developing HUS.

When Should I Worry About My Baby's Diarrhea?

True diarrhea in babies means a significant increase in the frequency and wateriness of stools compared to your baby's normal pattern. Breastfed babies normally have frequent, loose stools that can look like diarrhea but are completely normal. The biggest concern with actual diarrhea is dehydration. Most episodes of viral diarrhea resolve within 5-7 days. Seek medical attention if diarrhea is accompanied by blood, high fever, signs of dehydration, or lasts more than a week.

Is My Baby Dehydrated?

Dehydration in babies happens when they lose more fluids than they take in, usually from vomiting, diarrhea, fever, or inadequate feeding. Key signs include fewer than six wet diapers in 24 hours, no tears when crying, a dry mouth, sunken fontanelle (soft spot), and unusual drowsiness. Mild dehydration can often be managed at home with extra fluids, but moderate to severe dehydration requires prompt medical attention.

My Baby Looks Very Pale

Babies' skin color can vary naturally depending on temperature, activity, and genetics. However, true pallor (unusual paleness of the skin, lips, or nail beds) can sometimes indicate anemia, poor circulation, or an infection. If your baby looks noticeably paler than usual, especially in the lips, gums, inner eyelids, or palms, it is worth mentioning to your pediatrician.

Triage

Diarrhea Decision Tree

Evaluate diarrhea severity, dehydration risk, and when to act.

Milestone

Month-by-Month Development

Detailed monthly development guides from birth through 24 months.

Guide

When to Call the Doctor

General guide on when to call the pediatrician, visit urgent care, or go to the ER.

Frequently asked questions

Is hemolytic uremic syndrome (hus) in children normal?
Hemolytic uremic syndrome (HUS) is a serious condition characterized by a triad of hemolytic anemia (destruction of red blood cells), thrombocytopenia (low platelets), and acute kidney injury. It most commonly follows bloody diarrhea caused by E. coli O157:H7 infection. HUS is a medical emergency requiring hospitalization. With supportive care, most children recover kidney function, but early recognition and treatment are critical.
When should I call the doctor about hemolytic uremic syndrome (hus) in children?
Your child becomes pale, lethargic, or very irritable several days after the onset of bloody diarrhea, as these are warning signs of developing HUS Your child has significantly decreased urine output or has not urinated in 8-12 hours, especially following a diarrheal illness Your child develops unexplained bruising, petechiae (tiny red dots on the skin), or appears yellow (jaundiced) after a GI illness
When is hemolytic uremic syndrome (hus) in children normal?
Your child has a mild stomach bug with non-bloody diarrhea and is maintaining good urine output and hydration Your child had brief diarrhea that is resolving and they are returning to normal activity and eating Your child looks well, is not pale, and has normal energy levels during or after a GI illness
What causes hemolytic uremic syndrome (hus) in children?
Hemolytic uremic syndrome (HUS) is a serious condition characterized by a triad of hemolytic anemia (destruction of red blood cells), thrombocytopenia (low platelets), and acute kidney injury. It most commonly follows bloody diarrhea caused by E. coli O157:H7 infection. HUS is a medical emergency requiring hospitalization. With supportive care, most children recover kidney function, but early recognition and treatment are critical. Common explanations include: Your child has a mild stomach bug with non-bloody diarrhea and is maintaining good urine output and hydration. Your child had brief diarrhea that is resolving and they are returning to normal activity and eating.
What should I mention to my pediatrician about hemolytic uremic syndrome (hus) in children?
You should mention hemolytic uremic syndrome (hus) in children at your next visit if: Your child has bloody diarrhea, even if they seem well otherwise, as E. coli O157:H7 should be considered and a stool culture obtained. Your child seems more tired than expected during recovery from a stomach illness. You notice that your child is urinating less frequently than usual during a diarrheal illness.
Is hemolytic uremic syndrome (hus) in children normal at 0-6 months?
HUS is very rare in young infants. Breastfed babies are generally protected from the foodborne E. coli infections that trigger typical HUS. However, atypical HUS (not caused by E. coli) can occur at any age due to genetic mutations in complement regulation. Any infant with unexplained pallor, decreased urine output, or petechiae (tiny red spots on the skin) needs prompt medical evaluation.
Is hemolytic uremic syndrome (hus) in children normal at 6 months - 3 years?
This is the most common age group for typical (Shiga toxin-associated) HUS. It usually begins 5-10 days after the onset of bloody diarrhea from contaminated food or water. Warning signs that HUS is developing include pallor (the child looks washed out), decreased urine output, lethargy, and irritability even as the diarrhea may be improving. Small bruises or pinpoint red spots on the skin indicate low platelets. Do not give antibiotics or anti-diarrheal medications for suspected E. coli diarrhea, as these may increase the risk of HUS.
Should I go to the ER for hemolytic uremic syndrome (hus) in children?
Seek emergency care if your child becomes pale, lethargic, or very irritable several days after the onset of bloody diarrhea, as these are warning signs of developing HUS, or if your child has significantly decreased urine output or has not urinated in 8-12 hours, especially following a diarrheal illness. When in doubt, call your pediatrician's after-hours line for guidance.
Does hemolytic uremic syndrome (hus) in children go away on its own?
In many cases, hemolytic uremic syndrome (hus) in children resolves on its own, especially when your child has a mild stomach bug with non-bloody diarrhea and is maintaining good urine output and hydration. By 8 years+, while HUS can occur at any age, it is less common in older children. Older children may be better able to describe symptoms such as feeling very tired, having dark or reduced urine, or noticing bruises. Any child recovering from a diarrheal illness who develops these symptoms should be evaluated urgently. Atypical HUS (complement-mediated) should be considered in any child with HUS features without a preceding diarrheal illness.
AAPNIDDKCDC

References

  1. [1]American Academy of Pediatrics. Hemolytic Uremic Syndrome. Red Book: Report of the Committee on Infectious Diseases, 2024. AAP
  2. [2]National Institute of Diabetes and Digestive and Kidney Diseases. Hemolytic Uremic Syndrome in Children. NIH, 2023. NIDDK
  3. [3]Centers for Disease Control and Prevention. E. coli (Escherichia coli) and Hemolytic Uremic Syndrome. CDC, 2024. CDC

Doctor Visit Checklist

Bring this checklist to your next pediatrician visit to discuss Hemolytic Uremic Syndrome (HUS) in Children.

Things to mention

  • Describe when you first noticed hemolytic uremic syndrome (hus) in children and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your child has bloody diarrhea, even if they seem well otherwise, as E. coli O157:H7 should be considered and a stool culture obtained.
  • Mention if your child seems more tired than expected during recovery from a stomach illness.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

Observations to share

  • Your child has bloody diarrhea, even if they seem well otherwise, as E. coli O157:H7 should be considered and a stool culture obtained
  • Your child seems more tired than expected during recovery from a stomach illness
  • You notice that your child is urinating less frequently than usual during a diarrheal illness

Urgent signs to report immediately

  • Your child becomes pale, lethargic, or very irritable several days after the onset of bloody diarrhea, as these are warning signs of developing HUS
  • Your child has significantly decreased urine output or has not urinated in 8-12 hours, especially following a diarrheal illness
  • Your child develops unexplained bruising, petechiae (tiny red dots on the skin), or appears yellow (jaundiced) after a GI illness

My notes

From ismybabyalright.com — free, evidence-based baby health guides

All content follows our editorial policy and is reviewed against published clinical guidelines.

2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members

Related Resources

Diarrhea TriageWell-Baby Visit PrepEmergency ContactsBaby Tracker

Bottom line

Most cases of hemolytic uremic syndrome (hus) in children are normal. Talk to your pediatrician if your child becomes pale, lethargic, or very irritable several days after the onset of bloody diarrhea, as these are warning signs of developing hus.

Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.

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When Should I Worry About My Baby's Diarrhea?

True diarrhea in babies means a significant increase in the frequency and wateriness of stools compared to your baby's normal pattern. Breastfed babies normally have frequent, loose stools that can look like diarrhea but are completely normal. The biggest concern with actual diarrhea is dehydration. Most episodes of viral diarrhea resolve within 5-7 days. Seek medical attention if diarrhea is accompanied by blood, high fever, signs of dehydration, or lasts more than a week.

Is My Baby Dehydrated?

Dehydration in babies happens when they lose more fluids than they take in, usually from vomiting, diarrhea, fever, or inadequate feeding. Key signs include fewer than six wet diapers in 24 hours, no tears when crying, a dry mouth, sunken fontanelle (soft spot), and unusual drowsiness. Mild dehydration can often be managed at home with extra fluids, but moderate to severe dehydration requires prompt medical attention.

My Baby Looks Very Pale

Babies' skin color can vary naturally depending on temperature, activity, and genetics. However, true pallor (unusual paleness of the skin, lips, or nail beds) can sometimes indicate anemia, poor circulation, or an infection. If your baby looks noticeably paler than usual, especially in the lips, gums, inner eyelids, or palms, it is worth mentioning to your pediatrician.

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