Neonatal polycythemia

Alternative names
Hyperviscosity - newborn

Hyperviscosity is when blood flow is slowed and blocked because there are too many red blood cells in an infant’s blood.

Causes, incidence, and risk factors
Hyperviscosity results when the percentage of red blood cells (RBCs) in the infant’s blood is greater than 65%. This may result from various conditions that develop before birth, such as hypoxia, inherited diseases, and birth defects.

The high percentage of RBCs blocks the flow of blood in the smallest capillaries. This leads to tissue death from lack of oxygen. This blocked blood flow can affect all organs, such as the kidneys, lungs, and brain.

Infants with hyperviscosity may develop feeding problems, cyanosis, low blood sugar, jaundice, and other more serious findings.


  • Very ruddy red complexion  
  • Feeding problems  
  • Lethargy  
  • Seizures

Signs and tests

  • Bluish skin  
  • Low blood sugar  
  • Rapid breathing  
  • Respiratory distress  
  • Kidney failure  
  • Jaundice


  • Complete blood count for to determine RBCs/volume (hematocrit)  
  • Chem-20 to check blood sugar, BUN, creatinine  
  • Blood gases  
  • Urinalysis

A percentage of RBCs above 65% may be treated by raising the volume of body fluids or administering reduction transfusions, both of which can prevent the complications of hyperviscosity.

Expectations (prognosis)
The outlook is good in infants with mild hyperviscosity and in those with severe hyperviscosity that receive treatment.


  • Seizures  
  • Kidney failure  
  • Necrotizing enterocolitis  
  • Decreased fine motor control  
  • Strokes

Calling your health care provider
Call your health care provider if this condition is diagnosed at birth and you have additional questions.

Newborn infants are routinely monitored for their RBC levels. (The test is called a hematocrit). This enables quick detection of the condition.

Johns Hopkins patient information

Last revised: December 2, 2012
by Arthur A. Poghosian, M.D.

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