A parent’s guide to IBD blood tests and medication monitoring

If your child has Crohn’s disease or ulcerative colitis, blood tests can become a regular part of life with IBD.

You might hear terms like CRP, ESR, haemoglobin, ferritin, liver function, kidney function or white blood cell count and wonder what they actually mean.

Blood tests can feel overwhelming at first, but they are an important part of monitoring children with IBD. They can help your child’s healthcare team look for inflammation, check for nutritional problems, monitor the effects of medication and identify potential problems early.

Blood tests are only one part of the picture, though. Your child’s symptoms, growth, stool tests such as faecal calprotectin and, when needed, imaging or endoscopy may also be used to understand how their IBD is behaving.

🩸 Why does my child need blood tests?

Your child’s IBD team may use blood tests to:

• look for signs of inflammation

• check for anaemia or low iron

• monitor nutritional status

• check liver and kidney function

• monitor blood cell counts

• look for possible medication side effects

• check for signs of infection when appropriate

• monitor how your child is responding to treatment

• provide information alongside symptoms and other tests.

How often your child needs blood tests will depend on their age, IBD, treatment, symptoms and individual circumstances.

🔥 CRP and ESR: looking for inflammation

Two blood tests you may hear about are CRP (C-reactive protein) and ESR (erythrocyte sedimentation rate).

Both can provide information about inflammation in the body.

CRP

CRP is a protein that can increase when there is inflammation.

Your child’s IBD team may use CRP to help monitor disease activity and look at changes over time.

ESR

ESR is another blood test that can provide information about inflammation.

It can sometimes be useful alongside CRP and other results.

Does a normal CRP mean my child’s IBD is under control?

Not necessarily.

Blood tests are helpful, but they don’t tell the whole story. Some children with IBD can have significant intestinal inflammation without a large rise in blood inflammatory markers.

That’s why your child’s team may look at blood tests alongside symptoms, growth, stool tests such as faecal calprotectin and other investigations.

One blood test should never be interpreted in isolation.

🩸 Haemoglobin and the full blood count

A full blood count (FBC or CBC) looks at different types of blood cells.

Your child’s team may be particularly interested in:

• Haemoglobin — helps assess for anaemia.

• Red blood cells — carry oxygen around the body.

• White blood cells — are involved in the immune system.

• Platelets — can be affected by inflammation and other conditions.

Children with IBD can develop anaemia for several reasons, including inflammation and iron deficiency.

If your child is tired, pale, short of breath or struggling with energy, their healthcare team may consider whether anaemia or iron deficiency could be contributing.

🧲 Ferritin and iron

Ferritin is a measure related to the body’s iron stores.

Your child may have their ferritin and other iron measurements checked if their team is concerned about iron deficiency or anaemia. Iron can be particularly important in children because they are growing and need adequate iron for healthy development.

It’s possible for a child to have iron deficiency even when their haemoglobin is still within the normal range.

Your child’s IBD team can interpret iron results alongside inflammation and the other blood tests.

🧪 Liver and kidney function

Some IBD medications require monitoring of the liver and/or kidneys.

Your child’s blood tests may therefore include measurements that help assess how these organs are functioning.

The exact tests will depend on your child’s medication and individual circumstances.

If a result is outside the expected range, it doesn’t automatically mean that something is seriously wrong. Your healthcare team will look at the result in context and decide whether anything needs to be repeated, investigated or acted upon.

💊 Monitoring IBD medications

Different medications require different types of monitoring.

Some medicines may require more frequent blood tests when they are first started, while monitoring may become less frequent once treatment is established.

Your child’s healthcare team may monitor:

• blood cell counts

• liver function

• kidney function

• inflammatory markers

• nutritional markers

• medication-specific safety markers

• infection risk or previous infections, when relevant.

The exact monitoring plan depends on the medication, dose, age of your child and their health history.

Immunomodulators

Medicines such as azathioprine, 6-mercaptopurine and methotrexate can require regular blood monitoring.

For example, monitoring may include blood counts and liver tests because these medicines can affect blood cells or the liver.

Your child’s IBD team will tell you which tests are needed and how frequently they should be done.

Biologics and biosimilars

Biologic medicines and biosimilars may also involve monitoring.

Depending on the treatment, your child’s team may check blood tests, infection risk and inflammatory markers and may sometimes use medication levels or antibody testing when clinically appropriate.

Not every child needs every test.

Steroids

Corticosteroids such as prednisone or prednisolone are generally used to control active inflammation rather than as a long-term maintenance treatment.

When steroids are used, your child’s healthcare team may monitor their response and watch for treatment-related effects.

Never change or stop a steroid suddenly unless your child’s healthcare team has given you a specific plan.

🦠 Why are infection tests sometimes done before medication?

Before starting some IBD treatments, your child’s healthcare team may check for certain infections or previous exposure to infections.

Depending on the medication and your child’s circumstances, this can include screening for infections such as tuberculosis or hepatitis B.

This helps the healthcare team assess risks before starting treatment and decide whether any additional precautions are needed.

💩 What about faecal calprotectin?

Blood tests aren’t the only way to monitor IBD.

Faecal calprotectin is a stool test that can provide information about inflammation in the digestive tract.

Your child’s IBD team may use it alongside blood tests and symptoms to monitor Crohn’s disease or ulcerative colitis.

For many families, stool testing becomes part of routine IBD monitoring because it can provide information specifically related to inflammation in the gastrointestinal tract.

📈 What does it mean if my child’s results change?

It’s completely normal to feel worried when you see a result marked outside the laboratory’s reference range.

But one abnormal result does not necessarily mean that your child’s IBD is getting worse or that their medication isn’t working.

Your child’s team will consider:

• previous results

• current symptoms

• bowel habits

• blood or mucus in stools

• abdominal pain

• energy levels

• appetite

• weight and growth

• faecal calprotectin

• medication

• recent infections or illness

• other relevant tests.

Trends can be more useful than looking at one number on its own.

If you’re unsure what a result means, ask your child’s IBD team to explain it.

🔄 Why do doctors repeat the same blood tests?

You may notice that your child has the same blood tests again and again.

That’s often intentional.

Repeating tests allows the healthcare team to see whether things are:

Improving → staying stable → changing → or needing further investigation.

For example, your child’s team may compare inflammatory markers from several appointments rather than making a treatment decision based on one result.

Regular monitoring can also help identify medication-related problems early.

📅 How often will my child need blood tests?

There isn’t one schedule that applies to every child with IBD.

Testing frequency can depend on:

• the medication your child takes

• whether treatment has recently started or changed

• whether your child is having a flare

• previous blood test results

• other health conditions

• your child’s age

• local clinical guidelines and healthcare practices.

Your IBD team should tell you when your child’s tests are due.

If you’re unsure, ask:

“When is my child’s next blood test due, and what are we monitoring?”

📋 Keep a record of your child’s results

You don’t need to become an expert in every blood test.

However, keeping a simple record can help you see changes over time and make appointments easier.

You could keep track of:

• date of blood test

• CRP

• ESR

• haemoglobin

• ferritin

• iron studies

• liver tests

• kidney tests

• other medication-specific tests

• faecal calprotectin

• your child’s symptoms at the time.

You can ask your IBD team which results are most useful for you to keep track of.

💬 Questions to ask your IBD team

At your child’s next appointment, you could ask:

• Which blood tests does my child need?

• What is each test checking?

• Which results are most important for my child’s IBD?

• What were my child’s previous results?

• Are their results improving, stable or changing?

• Does my child’s medication require regular monitoring?

• How often should their blood tests be done?

• Does my child need faecal calprotectin testing too?

• What should we do if a result is abnormal?

• Who should we contact if we have questions about a result?

• When should the next tests be done?

❤️ Remember: the numbers are only part of the picture

It can be tempting to focus on individual numbers when you’re looking at your child’s blood results.

But IBD monitoring is about looking at the whole picture.

Your child’s symptoms, growth, energy, bowel habits, blood tests, stool tests and other investigations all help their healthcare team understand how their Crohn’s disease or ulcerative colitis is behaving.

And if you don’t understand a result, ask.

You don’t need to know what every number means before your child’s appointment. Your IBD team can explain what the results mean for your child and whether anything needs to change.

🌍 A note about medication monitoring

Medication monitoring can vary between medicines, children and countries. Different healthcare systems may use different testing schedules, laboratory reference ranges and monitoring protocols.

Always follow the monitoring plan provided by your child’s own IBD team.