Low blood counts

Children who receive cancer treatment commonly have low counts blood cells. The blood counts usually drop one week to 10 days after certain treatments are given and come back up in three to four weeks. 

Low white blood cells 

White blood cells fight infection. A normal white blood cell count is between 5,000 and 10,000 cells. The numbers on your blood count sheet may be written as 5.0 for a count of 5000. 

When the blood cell count drops below 1000 cells (less than 1.0), the risk of infection increases. In some cases, your child may be given medication to help increase the number of white blood cells in the bone marrow. 

If your child develops any of the following signs of infection, you should go to the hospital immediately. Don't wait until morning or for the clinic to open.


A fever may be a sign of a serious infection. If your child has a fever over 38 degrees Celsius, call the hospital right away. 

Children who receive cancer treatment are at high risk of getting an infection in the blood. If this happens and your child does not receive immediate medical attention, your child could become seriously ill. 

Anytime your child does not look well, call the hospital right away. Do not wait for the clinic to open. 

Shaking and other signs of infection

Even if your child does not have a fever - if they are shivering or shaking, bring them to the hospital immediately. 

  • pain, redness, pus or swelling anywhere in the body
  • pain, redness or pus around central line site or portacath 
  • sore throat
  • earache 
  • headache 
  • pain on urination or bowel movement 
  • diarrhoea 

Low haemoglobin (anaemia)

Red blood cells carry oxygen throughout the body. Haemoglobin shows how much oxygen the red blood cells are able to carry. Normal haemoglobin is between 120 and 160. Your child may require a blood transfusion if their haemoglobin falls below 70. 

Signs of low haemoglobin 

When haemoglobin is low, the body is not able to get enough oxygen throughout the body. Symptoms include:

  • tiredness
  • shortness of breath
  • headache
  • fast heart rate
  • pale skin, gums or lips 
  • dizziness. 

Blood transfusion

If your child requires a blood transfusion, a sample of their blood will be collected to match against the blood that they will be given.

This testing (cross-matching) is done each time blood is required and usually takes about 90 minutes. The hospital keeps stock of common groups, but depending on demand, blood products may need to come from the Australian Red Cross Blood Bank. This may mean that delays occur when waiting for a transfusion.

The blood given to your child will be packed cells (or PCs), which are concentrated red cells with the plasma and platelets removed. They will be given over several hours into a vein, either through a central line or port, or an IV in the arm.

Your child will be checked during the transfusion for signs of a reaction. Reactions may include shaking, hives (itching), redness or difficulty breathing.

Low Platelet Count (Thrombocytopenia)

Platelets stop bleeding in the body by forming clots. A normal platelet count is between 150 and 300 cells.

When the platelet count is low, your child is at risk of bleeding. A platelet transfusion may be given when your child's platelet count falls below 20.

Transfusions may be given at higher levels if your child is bleeding, having surgery, or has a brain tumour.

Signs of low platelets

If your child has a low platelet count, you may see any of the following signs:

  • bruising or petechiae (small, red, pinpoint freckles on the skin)
  • bleeding from the nose, gums, central line or port that doesn't stop with pressure applied  for 5 - 10 minutes
  • black stools or dark vomit may mean blood is in the stomach or bowel

Preventing bleeding

Putting anything in the rectum can cause bleeding or an infection. Do not:

  • give your child an enema, a suppository (medicine put into the rectum) or check a rectal temperature
  • give your child aspirin or ibuprofen (Nurofen, or Advil) unless you are told to do so by your doctor.

These medicines interfere with the way platelets work. Some over-the-counter medicines contain aspirin (salicylate) or ibuprofen. Read the labels and check with your doctor before giving your child any over-the-counter medicines.

Platelet transfusion

If your child requires a platelet transfusion, they receive a bag of platelets of the same blood group as theirs. Platelets do not need to be cross-matched against your child's blood.

Platelets are infused via a central line, portacath or a peripheral cannula over about one hour.

Occasionally allergic reactions to platelets may occur and include hives, rash, redness or fever. These reactions may require treatment with intravenous steroids and an anti-histamine 

Last updated Wednesday 26th June 2024