Life Fit Blog

How to Pass the DVLA CDT Test: A Clear, Step-by-Step Guide

Posted 2 weeks ago

If you’re working to regain your driving licence after a disqualification linked to alcohol, passing the DVLA CDT test is non-negotiable. This guide cuts through the noise to explain exactly what the test involves, how to prepare effectively, and what you need to do to maximise your chances of success.

What is the DVLA CDT Test?

The Carbohydrate Deficient Transferrin (CDT) test is a blood test used by the DVLA to assess alcohol consumption over the previous 2–4 weeks. It measures the percentage of transferrin—a protein that transports iron in the blood—that lacks carbohydrates. Elevated CDT levels signal heavy or chronic alcohol use, which can disqualify you from driving.

For high-risk offenders (those with serious drink-driving offences), this test is mandatory during the DVLA medical exam required to reinstate your licence.

Why the CDT Test Matters

The DVLA uses this test to confirm that drivers with a history of alcohol misuse are no longer drinking at harmful levels. Passing it is critical for:

  • Regaining your driving licence after disqualification.
  • Demonstrating abstinence or controlled drinking to the DVLA.
  • Avoiding delays in the licence renewal process.

How to Prepare for the DVLA CDT Test

Biomarker Zones

Green Zone
≤1.6%
Amber Zone
1.7-2.9%
Red Zone
≥3%

Optimisation Strategy

✓
Complete Abstinence

Minimum 4-week alcohol-free period for optimal CDT normalisation

↓
Controlled Reduction

80%+ reduction for 2-4 weeks (studies show CDT normalisation in this window)

Tips for Test Day Success

  1. Hydrate Well: Proper hydration makes blood draws quicker and easier.
  2. Avoid Alcohol Completely: Even a single drink can skew results.
  3. Bring Required Documents: This includes photo ID and any DVLA paperwork.
  4. Answer Questions Honestly: The DVLA doctor may ask about your drinking habits—dishonesty risks complications.

What Happens After the Test?

  • Passing Result (≤1.6%): The DVLA typically issues your licence within 15 working days.
  • Amber or Red Results: Expect further enquiries, which can delay the process by up to 90 days.

Final Steps to Ensure You Pass

  • Plan Ahead: Start reducing alcohol intake at least a month before the test.
  • Prioritise Liver Health: A balanced diet and avoiding alcohol support healthier CDT levels.
  • Seek Professional Guidance: If unsure about your habits, consult a GP or healthcare provider.

Key Takeaways

Passing the DVLA CDT test hinges on preparation and honesty. By understanding how the test works, adjusting your habits, and using tools like the Medichecks CDT Test to verify your levels, you can approach the process with confidence.

For those in Scotland’s Falkirk area, Life Fit Wellness provides a trusted local option for blood draws.