In medical dissertations, the literature review usually spans 15–30% of the total, shaped by scope, method, and program rules.
Planning the size of the review early saves rewrites later. You want enough depth to map the field, yet tight enough to keep the study front and center. The sweet spot in most medical theses lands in a clear range, and you can tune it with a few practical checks.
What “Length” Means In Practice
Length isn’t just a word count. It’s the space needed to define the clinical problem, group the evidence, show gaps, and lead into aims. Two projects with the same cap can need different amounts of context. A multi-system pathway study will demand more background than a focused device audit.
Set your target as a percentage of the whole, then translate that to words. For most medical topics, a 15–30% slice works for a narrative review that sets up original work. If you’re producing a stand-alone review as the thesis, the percentage will be higher by design.
Literature Review Length Targets By Thesis Size
The table converts common thesis caps to a review window you can aim for. Pick the row that matches your program cap or your personal target.
| Total Thesis Words | 15% Review (≈ words) | 30% Review (≈ words) |
|---|---|---|
| 30,000 | 4,500 | 9,000 |
| 40,000 | 6,000 | 12,000 |
| 50,000 | 7,500 | 15,000 |
| 60,000 | 9,000 | 18,000 |
| 75,000 | 11,250 | 22,500 |
| 80,000 | 12,000 | 24,000 |
| 100,000 | 15,000 | 30,000 |
Ideal Length Of The Literature Review For A Medical Thesis
Medical schools publish thesis caps that set the outer fence. One UK faculty lists a cap of 80,000 words for doctoral work in medical sciences (Newcastle thesis length). That leaves a wide envelope for the review, yet most candidates who craft a tight argument find the 12,000–24,000 range fits well for an 80k thesis.
A university writing guide also describes the review as a large early chapter and pegs its share near thirty percent on typical dissertations (Bath structure guide). That’s a helpful upper fence when you’re scoping a topic with many sub-fields.
When To Aim Near 15%
Lean toward the lower end when your study uses a narrow question, draws on a small, mature body of trials, or follows a registered protocol that keeps background brief. A lab-based project with a tight aim often benefits from a crisp, synthesis-first review that steps aside quickly for methods and results.
When To Aim Near 30%
Use the higher end when your topic spans multiple domains, the terminology varies across sub-disciplines, or the field has conflicting findings that need careful grouping. Mixed-methods work and service-evaluation theses often sit here.
How Review Type Changes The Size
Your approach drives length more than any single rule. Pick a plan, then budget words for each part.
Narrative Review Inside A Thesis
This is the common format in medical doctorates. You frame the topic, group the best evidence, and steer to a clear gap. Budget: 15–25% works for most projects with original data.
Systematic Review As A Chapter
If your chapter follows a full protocol with search strings, screening flow, quality checks, and meta-analysis, expect an extra few pages. Methods and results of the review itself add weight. Budget: 20–30% unless the thesis is review-only.
Thesis Built Around A Stand-Alone Review
Some programs allow a thesis that centers on a publishable review plus a reflective component. In that model, the review can exceed thirty percent because it is the main output. Follow your handbook on structure in that case.
Placement In An IMRaD-Style Thesis
Most medical theses use a structure that mirrors journal articles. The review sits after the general intro and flows into the study aims. Keep it as a single chapter unless your handbook asks for split sections. If you split, make the first half the conceptual map and keep the second half near the aims, so the logic stays tight.
Set A Target You Can Defend
Pick a number you can justify aloud in ten seconds. A clear defense sounds like: “The field is broad with conflicting trials, so I planned a 20% review to group methods and outcomes before I state the gap.” That kind of clarity helps in supervisory meetings and the viva.
Evidence-Based Checks To Right-Size Your Chapter
Use these checks while drafting.
Scope Check
Are you explaining anatomy, pathophysiology, and trial methods all at once? If yes, the topic may be too wide. Narrow the question or move methods detail to your chapter on design.
Redundancy Check
Does a paragraph repeat what your methods or discussion already cover? Trim the duplicate and leave a simple pointer instead.
Recency Check
Have you included the last two years of high-grade studies? If the field moves quickly, set an explicit cut-off and say why.
Balance Check
Do meta-analyses and large trials get more space than small case series? Weight space by evidence strength, not by citation count.
How Word Limits From Your School Affect The Plan
Doctoral caps differ across universities and degrees. Medical schools often sit near 75,000–80,000 words for MD or PhD work, excluding appendices and references in many cases. Always check your handbook and stick to the cap. If your program sets 80,000 words, a 12,000–20,000 review leaves ample room for methods, results, and a rigorous discussion.
Mid-Draft Tuning: A Simple Ratio Method
Here’s a quick way to tune length as the study evolves.
- Write a one-page aim and a one-page outline. Mark the core themes that the review must build.
- Draft the review to serve only those themes. Each subsection should land a clear message that feeds the aim.
- Count words at the end of each subsection. If one theme grows past its weight in the aim, prune or move details.
- Stop when the review cleanly funnels to the research questions. Don’t add summaries that repeat the intro or the discussion.
Common Pitfalls That Inflate The Chapter
Extended Textbook Background
A few tight paragraphs on physiology or device mechanics can be helpful; a long tutorial drags the chapter off course. Link out with a source if readers need deeper background.
Unfiltered Study Lists
Pages of one-line study summaries aren’t synthesis. Group by method, outcome, or patient group, then compare patterns.
Methods That Belong Elsewhere
Validation steps for your assay or survey should live in the methods chapter. Keep only the rationale in the review.
Quality Signals Examiners Expect
Examiners look for a map, not a catalogue. They want to see clear inclusion logic, a strong thread to the aims, and fair treatment of limits. Cite key trials and reviews, but keep the voice yours. Where reporting standards matter, align with the best-practice checklists for your study type.
Time Budget And Milestones
A clean review grows from steady, scheduled work. A workable plan is eight to twelve weeks of part-time writing for a 12k–18k chapter: two weeks scoping and search, four weeks drafting, two weeks pruning, and two weeks for supervisor feedback and rewrites.
Trusted Sources For Rules And Structure
University pages set hard caps and give structure tips. One medical sciences page lists an 80,000-word cap for doctoral theses, which helps you size the review window. A writing guide from another university frames the review as a large early chapter and pegs its share near thirty percent in a standard dissertation. Use these pages as anchor points, then follow your own handbook for local rules.
Calibrate With Exemplars
Browse recent theses in your field. Check their chapter lengths, not just the total. Note how authors group evidence and how soon they arrive at aims. Copy the structure logic, not the style.
What To Include, What To Skip
Must-Have Elements
- A short funnel from broad topic to precise gap.
- Clear grouping of the strongest evidence.
- Balanced treatment of conflicting findings.
- Short bridge into aims and hypotheses.
Safe To Leave Out
- Long lists of minor case reports unless the field is sparse.
- Basic textbook teaching that doesn’t move your argument.
- Definitions that a domain reader takes for granted.
Editing Moves That Cut Words Fast
- Turn three study summaries into one pattern sentence backed by grouped citations.
- Replace vague signposts with tight subheadings that match the message in the paragraph.
- Pull any paragraph that doesn’t land a claim tied to the aim.
- Move measurement detail to methods and leave a short pointer.
Second Table: Review Size Targets By Approach
Use these ballpark ranges to set expectations with your supervisor. Adjust to your cap and field.
| Approach | Typical Share Of Thesis | Notes |
|---|---|---|
| Narrative review within a thesis | 15–25% | Best for projects with original data. |
| Systematic review chapter | 20–30% | Methods and screening flow add space. |
| Review-led thesis model | 35%+ | When the review is the main product. |
One-Page Checklist Before You Lock The Length
- Does the chapter funnel cleanly to aims with no detours?
- Is the newest high-grade evidence covered and grouped?
- Do methods sit in the correct chapter, with only the rationale here?
- Does each subsection end on a claim that justifies your study?
- Is the word count inside the planned 15–30% window after trimming?
Bottom Line
For medical theses, a review that uses 15–30% of the whole is a safe, defensible target. Tune up or down based on scope, design, and your handbook. If you hit your aims early and keep repetition out, your chapter will land in range—and read well.