Researchers planning a study almost always ask the same practical question before anything else: how long will IRB review actually take, and when can data collection realistically begin? The honest answer is “it depends on the review category” — but within each category, timelines are predictable enough to plan around, provided the submission is complete and the study doesn’t require full-board scheduling or multi-site coordination.
This guide covers typical turnaround by review type, the specific factors that reliably add weeks to a timeline, and how to build a realistic project schedule around IRB review rather than treating it as an unpredictable black box.
Typical timelines by review type
Neither the Common Rule (45 CFR 46) nor FDA’s human-subjects regulations (21 CFR 50/56) set a mandated turnaround time for IRB review — timelines are set by each institution’s IRB and vary with staffing, meeting cadence, and submission volume. That said, published ranges from university and independent (commercial) IRBs converge on a consistent pattern:
- Exempt determination: typically 1-2 weeks for a complete submission (some IRBs report ranges out to 2-4 weeks during high-volume periods, such as the start of an academic term). Exempt determination doesn’t require full committee review — a single IRB staff member or designated reviewer confirms the study fits one of the Common Rule’s exempt categories (45 CFR 46.104) — so it isn’t tied to a meeting schedule and can, in principle, move as fast as staff capacity allows.
- Expedited review: typically 2-6 weeks, most commonly landing around 3-4 weeks for a complete, well-prepared submission. Expedited review covers minimal-risk research falling into one of the categories on the federal expedited-review list (published by OHRP) and is conducted by the IRB chair or one or more experienced reviewers designated by the chair, rather than the convened board — see CASRAI’s Expedited Review vs. Full Board Review comparison for how the two review pathways differ procedurally, including who can review, what triggers each pathway, and how continuing review differs between them.
- Full board (convened) review: typically 4-8 weeks, and often longer. Full board review requires a quorum of the convened IRB voting at a scheduled meeting, so the timeline is directly constrained by the committee’s meeting calendar (see below) on top of standard staff processing time. Institutions that meet monthly, or that don’t meet at all during summer/holiday periods, routinely push full board timelines toward 8-12 weeks for studies that miss a submission deadline.
These are general planning ranges drawn from published institutional and independent-IRB guidance, not a universal standard — every IRB sets its own internal processing targets, and it’s worth checking the specific IRB’s posted timeline (most post one) rather than assuming these figures apply exactly to a given institution.
What actually extends the timeline
The gap between the fastest and slowest end of each range above is almost always explained by one or more of the following, not by review-category ambiguity:
Incomplete or poorly prepared submissions
The single largest driver of delay industry-wide is a submission that isn’t ready for review on first pass — missing consent language required for the specific population, an inconsistency between the protocol and the recruitment materials, or a data security plan that doesn’t match what the protocol describes. Most IRBs run an initial administrative/pre-review triage step (commonly 3-5 business days) before substantive review even begins, and a submission kicked back at that stage restarts the clock rather than pausing it. Reviewer-requested revisions after substantive review add further rounds — each round typically costs another 1-3 weeks depending on how quickly the study team responds and whether the response itself requires further clarification. See CASRAI’s guide to the IRB application for what commonly gets a submission sent back before review even starts.
IRB meeting schedules (full board specifically)
A full board study isn’t reviewed continuously — it’s reviewed at the next meeting for which it qualifies, based on the IRB’s submission deadline (commonly a fixed cutoff, such as two weeks before the meeting date, to allow reviewer assignment and pre-reading). Missing that deadline by even a day typically means waiting for the following meeting, not the next available slot. Some IRBs — particularly at smaller institutions or those tied to an academic calendar — don’t meet during the summer or between academic terms, which can add a full quarter to a study’s timeline if the deadline is missed. Checking the convened board’s actual meeting calendar and submission deadlines before finalizing a project timeline is one of the highest-value planning steps a study team can take.
Multi-site and central/single-IRB (sIRB) coordination
Multi-site studies add a layer of timeline risk beyond a single-site submission: reliance agreements have to be executed between the relying institution(s) and the IRB of record, local context review still has to happen at each site (state law, institutional policy, local recruitment considerations) even when a central IRB holds primary review authority, and any site that responds slowly to the reliance-agreement or local-context step holds up the whole study’s start date. For NIH-funded multi-site studies, this coordination isn’t optional — NIH’s single-IRB policy (effective January 2018) generally requires domestic sites in a multi-site study to rely on one IRB of record, which shifts the coordination burden but doesn’t eliminate it. See CASRAI’s dictionary entry on Central IRB / Single IRB (sIRB) for how reliance review works mechanically. Realistic planning for a multi-site study should budget additional weeks specifically for reliance-agreement execution, separate from the substantive review timeline itself.
Study complexity and population-specific requirements
Research involving vulnerable populations (children, prisoners, pregnant women, individuals with impaired decision-making capacity), procedures carrying more than minimal risk, or novel/unfamiliar methodologies typically requires more reviewer discussion and more consent-form iteration than a straightforward minimal-risk survey study — which pushes both the review-round count and, in some cases, the review category itself (a study that might otherwise qualify for expedited review can require full board review if it involves greater-than-minimal-risk procedures or certain vulnerable populations).
Realistic planning guidance
- Build IRB review into the project timeline as an actual milestone with a range, not a placeholder. A defensible planning estimate is 2-3 weeks for exempt, 4-6 weeks for expedited, and 6-10 weeks for full board — measured from a genuinely complete first submission, not from when the study team starts drafting materials.
- Submit early relative to any hard deadline (a grant start date, a conference data-collection window, a co-investigator’s availability). Padding a timeline for at least one revision round is realistic for most first submissions, not pessimistic.
- Check the convened board’s meeting calendar before finalizing any project timeline that might require full board review — the submission deadline for the next meeting, not the meeting date itself, is the actual constraint.
- For multi-site studies, start the reliance-agreement process in parallel with protocol finalization, not after IRB-of-record approval — sequential handling of these two steps is one of the most common avoidable sources of delay.
- Use pre-submission consultation if the IRB offers it. Many IRBs offer an informal pre-review or office-hours consultation that catches the kind of completeness issues described above before they cost a full review round.
- Distinguish “review delay” from “reportable-event delay.” Once a study is approved and underway, a different clock applies to reporting unanticipated problems or noncompliance — see CASRAI’s guide to IRB Noncompliance & Unanticipated Problem Reporting for what must be reported, by whom, and on what timeline once a study is active, which is a distinct process from initial review timing.
Frequently asked questions
Does submitting for expedited review guarantee a faster timeline than full board?
Generally yes, because expedited review doesn’t depend on a committee meeting schedule — but the review category is determined by the study’s actual risk profile and procedures, not by which timeline the study team prefers. A study that doesn’t meet the federal expedited-review categories can’t be routed to expedited review just to save time.
Can an IRB fast-track a submission?
Most IRBs don’t offer a formal expedited-processing fee or queue-jump mechanism the way some ethics committees in other countries or industry-sponsored trial contexts do; the more reliable way to move faster within a given review category is a complete, well-prepared first submission and a fast turnaround on any requested revisions.
Does continuing review affect how long the initial approval takes?
No — continuing review is a separate, later process (re-review of an already-approved, ongoing study, historically required under the pre-2018 Common Rule for most non-exempt research and still required for some categories under the revised rule). It doesn’t affect how long the original approval takes, though the same meeting-schedule dynamics described above for full board review apply to it when it’s required.
Why do timelines vary so much between institutions?
IRB staffing levels, submission volume relative to reviewer capacity, meeting frequency, and whether the institution uses a fully electronic submission system all affect throughput. There’s no federal timeline requirement, so this variation is expected rather than a sign that a particular IRB is unusually slow.
Related CASRAI resources
- Expedited Review vs. Full Board Review: IRB Comparison — the procedural differences between the two review pathways.
- IRB Noncompliance & Unanticipated Problem Reporting — reporting timelines once a study is active, distinct from initial-review timing.
- The IRB Application: What to Include, How to Prepare It, and Why It Gets Sent Back — reducing the single biggest cause of review delay.
- IRB/REC Approval Process: What Needs Review and What Doesn’t — determining which review category a study falls into.
- Central IRB / Single IRB (sIRB) — how multi-site reliance review works.
- Continuing Review (IRB) — the ongoing re-review process for approved studies.
- IRB (Institutional Review Board) — foundational definition.
