Letters of Evaluation: What DO vs. MD Schools Actually Want to See

The mythology around letters of evaluation for MD vs. DO schools is mostly wrong.

You hear the same nonsense in every premed advising office: “Just get three science letters and a physician letter and you’ll be fine.” That advice is how people end up scrambling in August when they discover half their target DO schools require a DO letter, and several MD schools want a committee letter they never requested.

Let me break down what MD and DO schools actually look for in letters of evaluation—by content, by writer type, and by strategic value. Not the vague “strong letter” advice. The real criteria that adcoms talk about behind closed doors.

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MD vs. DO: The Structural Differences You Cannot Ignore

Start with the big picture. MD and DO schools live in the same application universe now—same residency Match, same USMLE/COMLEX landscape—but their letter expectations are not identical.

At a high level:

• MD schools mostly care about:

  • Academic rigor and comparison to peers
  • Evidence you can handle a heavy basic science load
  • Professionalism and reliability

• DO schools care about those same things but add:

  • Clear, credible understanding of osteopathic medicine
  • Genuine interest in DO specifically (not “backup plan”)
  • Often, a letter from a DO physician as a filter for seriousness

Here is what that looks like in practice.

Aspect	Typical MD Programs	Typical DO Programs
Total letters accepted	3–5	3–6
Committee letter	Preferred if available at many schools	Accepted, often optional
Science faculty letters	Frequently 2 required (biology/chem/physics)	Usually 1–2 required or strongly recommended
Non-science / other	Often 1 allowed or encouraged	Often 1–2 allowed (could be non-science or supervisor)
Physician letter	Some require or recommend (MD or DO)	Many *require* or prefer at least 1 DO letter
Research letter	Valued strongly at research-heavy MD schools	Helpful, but not central for most DO schools
Max letters read closely	Usually 3–4	Usually 3–4

Where people get burned: assuming MD rules apply to DO, or vice versa. They do not.

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The Core Problem: You Think “Strong” Is Enough

Most premeds focus on who to ask: “Is a letter from a PI better than one from my biochem professor?” Wrong starting question.

Adcoms care about what is in the letter and how credible the writer is to comment on it.

The ideal letter at both MD and DO programs shows three things clearly:

1. How you perform in a demanding environment compared to your peers
2. How you behave professionally: reliability, maturity, resilience
3. How you communicate and work with others (team, patients, lab, shadowing)

If the letter hits those three with specificity, they will take it seriously. If a letter just says “hardworking, passionate, caring,” it might as well not exist.

Now let’s break down specifics for MD and DO separately, then I will give you real strategies on who to pick and what to target.

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What MD Schools Actually Want To See

MD schools are ruthlessly academic in how they treat letters. There is usually one dominant question:

“Does this student have the intellectual horsepower and discipline to not fall apart in our curriculum?”

Everything else is secondary.

1. The MD Adcom Mental Model of a “Good” Letter

Here is how an MD adcom member silently scores a letter, whether they say it out loud or not:

• Is this writer in a position to judge academic performance?
• Does the writer compare the applicant to other students?
• Are there concrete behaviors, not just personality adjectives?
• Does the letter show sustained observation (months), not two weeks?
• Do I trust this writer? (Experienced faculty, course director, PI, advisor, etc.)

If the answer to most of those is “yes,” it is a useful letter.

2. The Science Faculty Letters: Non‑negotiable for MD

Most MD schools want at least two letters from science faculty (biology, chemistry, physics, sometimes math). Not TAs. Not lab managers. Actual instructors of record or course directors.

What they want those letters to show:

• Where you rank in the class. “Top 5% of 300 students I have taught in the last 5 years” is gold.
• Evidence you handle complex material. “Consistently at or near the top of a curve in an upper-division molecular biology course.”
• Work ethic with specifics. “Attended every office hour, routinely came prepared with questions beyond the scope of the course.”
• Professional behavior. “Handled a personal crisis during exam week by communicating early, making up work responsibly, and still finishing near the top of the class.”

The mistake I see? Students pick the “nice” professor who writes warm but vague letters, instead of the demanding one who can say: “She was one of two students who scored above 95% on the final in an infamously difficult course.”

You want the latter.

3. Committee Letters: Why MD Schools Like Them (And How They Read Them)

If your school offers a committee letter or a committee packet, most MD programs want you to use it. Because it simplifies their screening.

A committee letter tells them:

• Your institution has at least loosely standardized its evaluation
• You are likely not a disaster, or they would have flagged it
• They can skim fewer documents and still get a global picture

But here is the part premeds misunderstand: they still read individual letters inside the packet when they are interested in you.

I have watched faculty on committee jump straight to:

• The hardest science instructor’s letter
• The PI’s letter for research-heavy programs
• Any physician letter if the program emphasizes clinical maturity

Committee letters stitch together a narrative. The individual letters are where they look for real evidence.

4. Research Letters: MD Programs That Actually Care

At research-heavy MD programs (think UCSF, Penn, WashU, Hopkins), a research letter from a PI is almost essential if you did significant work.

Good research letters do three things:

1. Describe your technical skills and independence
2. Comment on your intellectual contribution, not just labor
3. Compare you to other undergrads and even early grad students or techs

Weak research letters simply say you “helped with experiments” and “were always on time.” That is not enough for serious research schools.

For MD programs that are not research‑obsessed, a PI letter can still carry weight if it talks about problem-solving, persistence, and curiosity. But they will not sacrifice an excellent science classroom letter just to have a research letter.

5. MD Physician Letters: When They Matter and When They Don’t

There is a widespread belief that every MD school “wants a doctor letter.” That is false.

Patterns I have seen:

• Some MD schools explicitly require or strongly recommend one physician letter (MD or DO) to verify clinical exposure.
• Many MD schools list physician letters as “optional” or in the “other” category. They carry variable weight, depending on content.

A useful physician letter:

• Documents substantial time: 40–100+ hours of volunteering, scribing, or shadowing
• Describes how you interact with patients, staff, and difficult situations
• Comments on your reliability, preparation, and maturity in a clinical context

A useless physician letter: “He shadowed me for a few days and seemed very interested and asked good questions.” This is just filler.

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What DO Schools Actually Want To See

DO schools want much of what MD schools want—academic strength, professionalism, maturity—but they have an additional agenda: filtering for applicants who actually understand and value osteopathic medicine.

The easiest place for them to do that? Your letters.

1. The DO Adcom Mental Model

Inside a DO admissions committee meeting, the silent questions reading your letters are slightly different:

• Can this student survive our curriculum and boards (COMLEX, and often USMLE)?
• Does this student show genuine understanding of osteopathic philosophy and practice?
• Or are they transparently an “MD reject” using DO as a backup?

That last one matters more than people admit.

2. The DO Letter Requirement: Not Just a Box

Many DO schools require or strongly prefer at least one letter from a DO physician. This is not cosmetic. It serves as:

• A proof of exposure: you have spent real time in a DO setting
• A cultural filter: the DO confirms that you “get it” and fit
• A seriousness signal: you went out of your way to find a DO, not just default to the MD in your hometown

A high-impact DO letter should include:

• Length and nature of contact: “She shadowed in my clinic weekly for three months,” or “We worked together in an OMT-focused family medicine practice for 60 hours over the summer.”
• Evidence of understanding osteopathic care: “He specifically asked about how I integrate OMT and preventive care,” or “She observed and then could articulate the rationale for osteopathic structural exams.”
• Comments on fit with osteopathic values: holistic care, patient communication, interest in underserved populations, prevention, continuity.

A DO letter that just says, “He shadowed me; he is very interested in medicine,” does almost nothing. DO adcoms have seen thousands of those.

3. Science Letters at DO Schools: Still Crucial

Here is where some applicants get sloppy. They assume DO schools are “less academic,” so the content of science letters matters less. Wrong.

DO curricula are still heavy in basic sciences, and DO programs are under pressure to maintain or improve COMLEX/USMLE pass rates.

So DO schools want:

• At least one strong science faculty letter confirming you can handle dense material
• Evidence you can rebound from difficulty (especially if GPA is not stellar)
• Comments on work ethic, remediation, and persistence

I have seen DO adcoms value a science letter that says, “He struggled early, sought help, and steadily improved into the top third of the class” more than one that just says, “She got an A and was always quiet but respectful.”

They are very sensitive to trajectory and resilience.

4. Non-Science and Supervisor Letters: Where DO Schools Look for “Whole-Person” Evidence

Osteopathic schools talk constantly about holistic care and whole-person development. That is not marketing fluff; it bleeds into how they read letters.

Non-science or supervisor letters (employer, coach, service org leader) can carry more weight at DO programs when they show:

• Long-term service or work commitments
• Leadership in hands-on, people-facing roles (EMS, CNA, MA, scribe lead, resident assistant)
• Evidence of empathy, patience, and communication with vulnerable populations

Is this “touchy-feely”? Sometimes. But it is also entirely rational for a model of care that emphasizes ongoing patient relationships and primary care.

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Content: What The Best Letters Actually Say (For Both MD and DO)

Forget titles for a moment. Strip away MD vs. DO. Strong letters share some very specific traits.

1. Specific Behaviors, Not Generic Praise

Adcom members are numb to adjectives. “Hard-working,” “passionate,” “empathetic,” “team player.” Everyone is all those things on paper.

What stands out:

• “She consistently stayed 30 minutes late after every clinic session to review cases and follow up on pending lab results without being asked.”
• “When our PCR machine failed the day before data collection, he came in on a Sunday, coordinated with another lab, and salvaged the project.”
• “During an emotionally charged family meeting, she quietly identified that the patient’s daughter had not understood the prognosis and gently restated it in more accessible language.”

Specific, observable actions. Not vibes.

2. Comparisons to Peers

Adcoms want calibration. They want to know: are you just good in isolation, or are you objectively strong?

High-yield phrases:

• “Among the top 5% of students I have taught in the last decade”
• “Stronger than most first-year residents I have supervised in terms of professionalism and communication”
• “In the top three undergraduates I have mentored in my lab over 15 years”

Vague rankings like “above average” are almost useless.

3. Red Flag Management

Here is the part nobody tells you: letters can quietly address and neutralize red flags.

Examples:

• GPA trend: “He earned a C+ in my course, but returned the following semester to retake a more advanced version, sought regular feedback, and ultimately performed at the top of the class.”
• Withdrawal or LOA: “During a period of family illness, she stepped away briefly from research but communicated early and maintained her responsibilities as much as possible. Upon return, she quickly reestablished herself as a core member of the team.”

When MD and DO schools see honest, specific accounts of growth, they trust the application more.

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Strategy: Building a Letter Portfolio That Works for Both MD and DO

You are not applying to one school. You are applying across a range of MD and DO programs, each with slightly different rules. You need a modular letter set that can be configured to meet them.

Let me give you a practical structure.

1. Your “Core Three” Letters

For most applicants, the core that works for both MD and DO:

1. Science Faculty #1 – upper-level biology, biochemistry, or physiology
2. Science Faculty #2 – another major science course (chem, physics, etc.) or math/statistics if allowed
3. Clinical or PI Letter – depending on your profile

If you are more research-heavy and targeting research MDs:
Make #3 a PI letter.

If you are more clinical/service-heavy and targeting a lot of DO schools:
Make #3 a physician or clinical supervisor letter.

2. Additional Letters for Flexibility

On top of your core three, target 1–2 more letters that you can selectively send:

• DO Physician letter – mandatory or strongly preferred for many DO schools
• Non-science professor – some MD schools like seeing performance in humanities/social science
• Employment/service supervisor – for applicants with heavy work or long-term volunteering

ERAS-like overkill (8–10 letters) is pointless for med school. Focus on 4–6 well-chosen, high-content letters and then customize which 3–4 go to which school.

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Timing and Mechanics: How to Not Sabotage Yourself

I have seen too many applicants with objectively strong profiles end up mediocre because their letters were rushed or poorly chosen.

1. When to Ask

You ask for letters when:

• You have performed well enough for the writer to say something substantial
• You are still fresh in their mind
• You can give them plenty of lead time (1–3 months before you actually need letters in AMCAS/AACOMAS)

For typical timelines:

• If you apply in June: start asking in February–April of that year
• For DO physician letters built off shadowing: ask near the end of your scheduled shadowing block, not after three casual days

2. What to Give Letter Writers

If you want good letters, you cannot just say, “Can you write me a strong letter?” and walk away. That is lazy.

Give them:

• An updated CV or resume
• A short, 1–2 page “Letter Info Sheet” (bullet style) with:
  • Your intended specialties of interest
  • Why MD, why DO, or both
  • Specific projects or interactions you had with them
  • Any personal context: GPA trend, major work commitments, family obligations
• Draft of your personal statement or at least a one-paragraph narrative of your path toward medicine

You are not scripting their letter. You are giving them material to work with so they can produce specifics.

3. Waiving Your Right to View Letters

Always waive your right to see your letters (FERPA). MD and DO schools both assume:

• Confidential letters = more honest = more credible
• Non-waived letters = potential red flag

You want your letters to carry maximum weight. Waive.

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Common Failure Patterns I See Every Cycle

If you want to avoid being the cautionary tale in August, understand these predictable mistakes.

1. No DO Letter for DO Schools That Require It

Yes, some DO schools will say “DO or MD letter accepted.” But many explicitly say “DO preferred” or “DO required.” People still ignore this.

Result: You get quietly filtered into the “maybe” or “no” pile regardless of stats.

Solution: If you are applying to more than ~3–4 DO programs, get a DO letter. Period.

2. All Letters from Non-Teaching Roles

Three letters from:

• Your volunteer coordinator
• Your job supervisor at Starbucks
• The coach from your intramural team

And zero from science faculty.

This kills you at MD schools and hurts you at DO programs. You look like you are avoiding academic scrutiny.

3. Using “Famous” Names Who Barely Know You

That letter from the department chair who met you twice? Or the MD who is chief of surgery but only saw you for six hours in an OR? Nearly useless.

Adcoms read those and can smell a “favor letter” in two paragraphs. No detail, no depth, lots of prestige filler. It does not move the needle.

You want depth and specifics from a mid-level professor far more than a one-paragraph generic endorsement from a big name.

4. Five Medium Letters Instead of Three Excellent Ones

Schools usually allow up to 5 or 6 letters. Students panic and think, “More is better.”

It is not. Committees reading your file are human. They lock onto 2–3 letters at most. If you flood them with mediocre, repetitive letters, you dilute your impact.

Better to have:

• 1 devastatingly strong science letter
• 1 specific, detailed clinical or DO letter
• 1 strong supporting science or PI letter

Than 6 letters that all say “hard-working, smart, a pleasure to have.”

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How This Plays Out In Real Files

To make this concrete, let me show you two composite examples I have seen versions of.

Applicant A: 3.72 cGPA, 512 MCAT, Applying MD + DO

Letters:

• Biochem professor: “Top 10% of 250 students, attended office hours regularly, led group study sessions, strong improvement from midterm to final.”
• PI of 1.5-year research: “One of the best undergraduates I have mentored; independently designed control experiments, co-author on upcoming manuscript.”
• DO family physician: “Shadowed ~80 hours over 4 months; consistently arrived early, engaged thoughtfully about OMT and primary care, connected well with patients and staff.”

Result pattern:

• MD: considered at a wide range of mid-tier programs, serious look at some research schools
• DO: seen as high-value applicant, assumed genuinely interested in DO because of the DO letter quality

Applicant B: 3.85 cGPA, 516 MCAT, Applying MD + DO

Letters:

• Organic chem professor: “He was in my large lecture, sat in the front, got an A.” No ranking, no specifics.
• Volunteer hospital coordinator: “She is nice, always on time, very compassionate with patients.”
• MD neurosurgeon: “Shadowed for two half-days, interested in neurosurgery, asked good questions.”

Result pattern:

• MD: screened in at many places because of stats, but letters do not help differentiate. When compared to others, gets passed over post-interview for stronger narratives.
• DO: seen as MD-leaning, no DO contact, questionable commitment to osteopathic path. Several DO schools with DO-letter preference do not seriously consider.

Stats are not everything. Letters quietly shape how risk-averse committees choose between hundreds of applicants with similar numbers.

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Final Distillation: What MD vs. DO Schools Actually Want

Keep this short list in your head when you choose and cultivate your letter writers.

1. MD schools prioritize rigorous academic letters that clearly rank you among peers and demonstrate you will not collapse under a heavy science curriculum. Research letters matter more at research-heavy programs, but only when they demonstrate real intellectual contribution.

2. DO schools want proof you can handle the work plus evidence you understand and genuinely value osteopathic medicine, ideally through a substantial, specific letter from a DO physician. They also pay real attention to service, resilience, and longitudinal commitment described in non-science and supervisor letters.

3. Across both, generic praise is background noise. Specific behaviors, comparisons to peers, clear descriptions of growth, and credible writers who actually know you—that is what gets discussed in the room when your file comes up.