If you’ve found a clinical trial that looks promising, one of your first questions is probably:
Browse currently recruiting clinical trials by condition and location
Compare study options, check eligibility, and reach out to study teams when you’re ready.
“How long will it take before I can actually start?”
The answer depends on several factors, including the type of trial, your medical history, and how quickly eligibility can be confirmed. While some patients move through the process in a few weeks, others may wait longer due to screening requirements or enrollment limits.
Understanding the timeline can help you plan ahead and reduce uncertainty.
Step 1: Submitting Your Interest
(A Few Minutes to a Few Days)
The process usually begins when you:
- Fill out an online interest form
- Call the study site
- Speak with your doctor about a trial
At this stage, you are simply expressing interest — you are not yet enrolled.
Some study teams respond within a few days. Others may take 1–2 weeks, depending on staffing and how many applicants they’re reviewing.
Step 2: Pre-Screening
(Several Days to 2 Weeks)
If the study team contacts you, the next step is typically pre-screening.
This may involve:
- A phone interview
- Basic medical history questions
- Reviewing current medications
- Confirming diagnosis details
Pre-screening helps determine whether it’s worth moving forward to formal screening.
If you don’t meet basic eligibility criteria, the process may stop here. If you qualify, you’ll move to the next stage.
Step 3: Screening Visit
(1–4 Weeks)
The screening phase is where most of the time is spent.
During screening, the study team may:
- Review your medical records
- Perform lab tests
- Conduct imaging (if needed)
- Evaluate vital signs
- Confirm specific inclusion and exclusion criteria
Some trials require multiple screening appointments. Lab results may take several days to return. In certain cases, additional documentation from your primary doctor may be required.
For many trials, this phase lasts 1 to 4 weeks.
Step 4: Enrollment and Randomization
(Days to 2 Weeks)
If screening confirms you’re eligible, you’ll be officially enrolled.
In some trials:
- You begin treatment shortly after enrollment
- You may be randomly assigned to a treatment group
- A baseline visit may be scheduled before treatment starts
The time between eligibility confirmation and starting treatment can vary from a few days to a couple of weeks.
Why Does It Sometimes Take Longer?
Several factors can delay enrollment:
1. Waiting for Test Results
Certain lab or imaging results may take time.
2. Study Enrollment Limits
Trials have a limited number of spots. Even if you qualify, you may need to wait if enrollment is paused or nearly full.
3. Complex Eligibility Criteria
Some trials require very specific health markers or medication histories.
4. Coordination With Your Current Care
If you need to stop a medication before starting the trial (a “washout period”), this can add extra time.
Can You Speed Up the Process?
While you can’t control every step, you can help avoid delays by:
- Having copies of your medical records ready
- Preparing a list of current medications
- Responding quickly to study team communications
- Asking about expected timelines early
Clear communication with the study coordinator can also help you understand where you are in the process.
What If I Need Treatment Immediately?
If your condition requires urgent treatment, discuss this with your doctor before waiting for a trial.
Clinical trials follow structured protocols and cannot always move as quickly as standard medical care. In some cases, starting standard treatment first may be recommended while you explore trial options.
Your healthcare provider can help you balance timing and medical need.
Typical Timeline Overview
While every study is different, here’s a general estimate:
- Initial contact → 1–2 weeks
- Pre-screening → a few days to 2 weeks
- Screening phase → 1–4 weeks
- Enrollment to first treatment → days to 2 weeks
Total time: Often 2–6 weeks from first contact to starting treatment. (Some trials may move faster. Others may take longer.)
What Happens If You’re Not Approved?
If you don’t qualify, it doesn’t mean you won’t qualify for other trials.
Different studies have different eligibility requirements. You may still be a strong candidate for another research opportunity.
Explore Clinical Trials That Match Your Timeline
If you’re considering a clinical trial, it can help to compare different studies and ask about expected enrollment timelines.
Not sure if you’ll qualify for a study? Before applying, learn how eligibility criteria work and what researchers look for in participants.
FAQs
How long does screening usually take?
Most screening phases last between 1 and 4 weeks, depending on required tests and documentation.
Can I be approved immediately?
It’s rare to start treatment immediately. Even fast-moving trials typically require at least some screening and paperwork.
Why didn’t the study team contact me right away?
Study sites may receive many applications. Delays can happen due to volume, staffing, or enrollment pauses.
Can I apply to more than one clinical trial at the same time?
In many cases, yes — but you can usually only participate in one trial at a time. Always inform study teams if you’re applying elsewhere.