Better2Know Inflammation & autoimmunity

C3 Protein Test

This blood test measures complement C3, a protein involved in immune system activity. It's commonly used to help assess autoimmune or inflammatory conditions, such as lupus, alongside other tests.

Sample
Blood
Collection
Venous draw at clinic or nurse visit
Results in
1 day
Biomarkers
1
Tests for
  • C3

Test specifications

Provider
Better2Know
Sample type
blood
Collection method
venous draw at clinic or nurse visit
Turnaround time
1 day
Biomarkers tested
1
At-home test
No
Doctor reviewed
No
Gender focus
Both

What's tested

1 biomarker as listed by Better2Know.

  • C3

About this test

Complement C3 is a protein that plays a central role in your immune system's response to infection and in clearing damaged cells. This test measures how much C3 is in your blood; low levels can be linked to increased autoimmune activity or a deficiency, while high levels can point to inflammation or infection. It's commonly used alongside other tests to help assess conditions such as lupus or other autoimmune or inflammatory activity, and to monitor treatment for these.

We do not have a directly comparable rival test on file for C3 specifically, so we cannot compare it against named peers. Against the wider set of inflammation tests we track, it is priced well above the typical rate, at 41% over the median for a test of this size, which is the main driver of its relatively low value for money score.

It scores well for clarity, with the sample type, what is measured and the turnaround clearly published, and around the middle for clinical depth as a single, specific marker. It loses marks on results and follow-up because a doctor does not review the results as standard, which matters here since interpreting an abnormal C3 result usually needs clinical context.

Who is it for?

This suits you if a clinician has suggested checking your complement C3 level, for example as part of investigating suspected lupus or another autoimmune or inflammatory condition, or to monitor a known condition. It is a specific, single-marker test rather than a broad immune or inflammation panel.

We do not have a directly comparable rival test on file, so if you want wider immune or inflammation markers alongside C3, it is worth checking whether a broader autoimmune or inflammation panel would suit you better and comparing the prices.

How it works

A trained healthcare professional takes a venous blood sample at a clinic, or you can arrange a home nurse visit, and the sample is analysed to measure the concentration of C3 protein. Results are typically available within one working day, and you receive a report showing your C3 level; the provider does not state that a doctor reviews the results as standard, so any follow-up on an abnormal result would need to be arranged separately.

Pros & cons

Pros

  • Measures a specific immune marker useful alongside other autoimmune tests.
  • Results are typically available within one working day.
  • Can be arranged as a home nurse visit rather than a clinic appointment.

Cons

  • Priced 41% above the median for the inflammation tests we track.
  • Results come without routine doctor interpretation.
  • A single marker test rather than a broader immune or inflammation panel.

Our editorial score

Compare Health Test Score Immune-marker test priced 41% above typical
Editorial confidence: 9.0/10

The C3 Protein Test is a £125 blood test that measures complement C3, a protein used to help assess immune system activity. It prices 41% above the £88.63 median for the inflammation tests we track, and we do not have a directly comparable rival test on file. Results are typically ready within one working day, though a doctor does not review them as standard.

Score breakdown

  • Clarity and documentation 9.0/10

    The listing publishes a detailed description, the full biomarker list, a stated turnaround, clear collection options, the sample type; it does not state what the report looks like.

  • Clinical depth 6.4/10

    1 biomarkers, placing it in the 32nd percentile of inflammation tests we track.

  • Collection convenience 6.0/10

    Requires a venous draw at a clinic; a home nurse visit is offered; results in around 1 days, well ahead of the inflammation norm of 4.

  • Results and follow-up 3.0/10

    Results are not doctor-reviewed and no consultation is included; the provider does not describe the report format.

  • Trust signals 6.5/10

    Trustpilot 4.2 from 775 reviews; CQC registered; trading 18+ years.

  • Value for money 4.4/10

    £125.00 against a median of £88.63 for the 26 similarly sized inflammation tests we track (+41%).

Calculated 13 September 2026 from the facts we hold about this test and provider, using our published scoring formula. Scores are not hand-edited.

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