Fourth‑Year Calendar: How to Slot Sub‑Is for FM, Peds, and Med‑Peds

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It is early March of third year. You finally admitted to yourself that FM, Peds, and Med‑Peds are the real contenders. Your classmates are loudly arguing about Derm vs ENT. You are quietly staring at the lottery form for fourth‑year rotations, trying to answer one question:

How do I slot my sub‑Is so I do not screw up all three options?

Let me walk you through the calendar. Month by month. What should be locked in early, what can float, and what is flat‑out a bad idea.

We are going to assume:

• You are applying in the regular ERAS cycle.
• Your school year runs roughly July–June.
• You are serious about at least two of: FM, Peds, Med‑Peds (or you want to keep them open).

If your specific dates are off by a few weeks, the logic does not change. You just shift the blocks.

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Big‑picture timeline: MS3 spring → Rank list

Start with the year skeleton. Then we will zoom into each chunk.

Fourth Year Sub-I Planning Timeline

Period	Event
MS3 Spring - Feb-Mar	Decide target specialties, meet advisors
MS3 Spring - Mar-Apr	Identify programs, plan Step 2 date
Early MS4 - Jul-Aug	Home Sub-I core, Step 2 CK
Early MS4 - Aug-Sep	Away Sub-I or second Sub-I
Application - Sep	ERAS submission
Application - Oct-Nov	Optional late Sub-I, interviews start
Interview/Rank - Dec-Jan	Interviews peak, light rotations
Interview/Rank - Feb	Final rank list

Here is the core principle:
You get at most 2–3 sub‑Is that actually matter for these specialties. Use them deliberately:

• 1 core “home” sub‑I in your top specialty (FM, Peds, or Med‑Peds).
• 1 second sub‑I in your other serious option (or a different setting in the same field).
• Optional 3rd: away rotation where you truly want to match.

Everything else (electives, chill rotations, research) is padding around those.

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Step 0 (MS3 Feb–April): Set constraints before you slot anything

At this point you should NOT be picking exact months. You should be locking in constraints.

Weeks 1–4 (late winter MS3): Clarify priorities

By the time you are finishing Peds or FM on core rotations:

• Meet with:
  • Your FM advisor (or departmental student advisor).
  • A Peds faculty member you actually like.
  • At least one Med‑Peds resident or PD if your school has a program.

Ask concrete questions:

• “If I am debating FM vs Med‑Peds, where should my first sub‑I be?”
• “Do you expect an away rotation for Med‑Peds?”
• “How heavy do you weigh home letters vs away letters?”

What usually emerges:

• FM: Away rotations are nice but absolutely not required. Strong home sub‑I is enough.
• Peds: Similar. Home Peds sub‑I plus one good letter is usually plenty.
• Med‑Peds: Much more program‑specific. Many applicants do 1 Med‑Peds sub‑I away to signal commitment.

Weeks 5–8: Decide Step 2 CK timing

You cannot seriously plan sub‑Is without locking Step 2 CK into a window.

Typical best‑case for FM/Peds/Med‑Peds:

• Take Step 2 CK in late June or early July, right after MS3 ends.
• Or first half of July during a light elective.

Do NOT:

• Stick Step 2 in the middle of your first sub‑I. You will be mediocre at both.
• Schedule Step 2 after August if your Step 1 was weak. These specialties are holistic, but programs still like seeing Step 2 early.

Common Step 2 CK Timing for Primary Care Applicants

Category	Value
June	40
July	35
August	15
September or later	10

Target: Know your Step 2 test week before you commit sub‑I months.

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Step 1 (Big Decision): Which specialty gets the first sub‑I?

Here is the honest hierarchy:

• Most decisive: Med‑Peds. It is niche, relatively small, and very letter‑driven.
• Next: Peds.
• Least stressed about letters: FM (still cares, but has more flexibility and more program volume).

So if you are:

• Peds vs Med‑Peds → Do Med‑Peds first, Peds second.
• FM vs Med‑Peds → Do Med‑Peds first, FM second.
• FM vs Peds only → Pick whichever one you are leaning toward for first sub‑I, do the other immediately after.

I have seen people hedge too long, put Med‑Peds last, and then regret not having a strong Med‑Peds letter by ERAS launch. Do not do that.

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Sample Year Layouts (choose what matches you)

Use these as templates, not commandments.

Profile	Jul	Aug	Sep	Oct
FM > Peds	FM Sub-I (home)	Peds Sub-I	Elective / outpatient FM	Light elective / interview prep
Peds > Med-Peds	Med-Peds Sub-I (home/away)	Peds Sub-I (home)	Elective Peds / NICU	Light elective
Med-Peds focused	Med-Peds Sub-I (home)	Med-Peds or Peds Sub-I (away)	FM or Peds elective	Light elective

We will break down the logic month by month.

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July–August: Anchor sub‑Is + Step 2

This is the spine of your application.

If you can take Step 2 before July

Best scenario. Then you can hit the ground running.

Option A: Leaning Med‑Peds

• July: Med‑Peds Sub‑I (home if you have a program)

  • Show your home Med‑Peds people who you are.
  • Secure 1–2 letters (often from Med‑Peds faculty who also do Peds or IM).

• August: Peds or Med‑Peds Sub‑I (away)

  • If no home Med‑Peds: this becomes your critical away.
  • Choose a program where you would actually be happy matching, not just a “name brand.”

At this point you should:

• Have at least 1 strong Med‑Peds–flavored letter.
• Be on the radar of at least one Med‑Peds program.

Option B: Leaning Peds, keeping FM in play

• July: Peds Sub‑I (home)
• August: FM Sub‑I (home or local affiliate)

Benefits:

• You will quickly feel which patient population / clinic style fits you.
• You will have one Peds letter and one FM letter ready for both application tracks.

Option C: FM‑leaning, others as backups

• July: FM Sub‑I (home clinic or inpatient service)
• August: Peds or Med‑Peds Sub‑I (if you are truly considering them)

Family medicine programs do not need you to have an early Peds or Med‑Peds sub‑I. But if those are serious contenders, slot them in early so letters are ready.

If Step 2 is in early–mid July

Then you need to protect that exam:

• July: Light rotation (outpatient elective, research, or a chill required clerkship) + Step 2
• August: First sub‑I (Med‑Peds or Peds or FM depending on your priority)

This pushes your sub‑Is a month later, but it is still acceptable. Just be sure at least one sub‑I finishes by the end of September.

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September: Last meaningful month for letters

By this point you should be turning the ERAS application in or polishing it. You can still squeeze one more high‑yield sub‑I here.

At this point you should:

• Already have at least one sub‑I completed (July or August).
• Know your ranking between FM, Peds, and Med‑Peds.

Smart uses of September:

1. Second core sub‑I

   • If July was Med‑Peds, August was Peds → September can be FM.
   • If July was FM, August was Peds → September can be Med‑Peds away.

2. Targeted away rotation

   • Med‑Peds: A September away at a top‑choice program can still give you a letter. Some programs will accept letters that arrive slightly later.
   • Peds: Same, but less critical than Med‑Peds.

3. Clinic‑heavy elective in your top specialty

   • If letters are already solid, a continuity clinic month in FM or Peds reinforces your story without the intensity of a sub‑I.

Avoid:

• Starting your first sub‑I in September. That is late. Your letters might not land in time at all programs, especially those that review early.

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October–November: Optional polish vs overkill

Once ERAS is in and interviews start trickling in, sub‑Is lose some marginal value. They still matter for:

• Late letters.
• Strengthening your skills before residency.
• Making a good last impression at a specific institution.

But they are not as critical as July–September.

Good uses of Oct–Nov:

• Sub‑I #2 or #3 for skill‑building, not just for letters:

  • Example: July Med‑Peds (home), August Peds (home), October FM inpatient month.
    You now have broad, relevant experience.

• Sub‑I at a local program where you might SOAP if things go badly. Harsh, but real.

• Mixed Med‑Peds experiences:

  • 2 weeks adult wards + 2 weeks Peds wards.
  • Or a combined clinic month if your school offers it.

Things I have seen go poorly:

• Students doing their first and only FM/Peds/Med‑Peds sub‑I in October and then being surprised when interview invites are thin. Your performance there will barely influence that season.

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December–January: Interviews dominate

Your calendar here should be intentionally soft.

At this point you should:

• Be interviewing in at least one of FM, Peds, or Med‑Peds.
• Have your letters all in.

Rotations that fit well:

• Light outpatient electives in your chosen field.
• Student teaching electives.
• Research or QI elective you can do remotely or flexibly.

Do not:

• Schedule a heavy inpatient sub‑I while you have 8–10 interviews. Everyone suffers: you, your team, and your applicants scores when you are absent.

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Specific tracks: how to balance FM, Peds, Med‑Peds

Let us lay out concrete “tracks” depending on your situation.

Track 1: “I am 70% Med‑Peds, 30% Peds”

Goal: Convince Med‑Peds you are serious, but keep standard Peds viable.

Recommended calendar:

• July: Med‑Peds Sub‑I (home)
• August: Peds Sub‑I (home or respected children’s hospital)
• September: Med‑Peds away at a realistic top choice
• October: Light elective (outpatient Peds / Med clinic)
• November: Research or teaching elective

Letters:

• 2 Med‑Peds‑leaning letters (often from Med‑Peds faculty with IM/Peds appointments).
• 1 pure Peds letter (from the August Peds sub‑I).
• 1 chair / department letter as required.

Track 2: “I am split between FM and Peds”

Here you can be a bit more relaxed. Both fields are flexible and value similar traits.

Recommended calendar:

• July: Peds Sub‑I (home)
• August: FM Sub‑I (home or affiliate)
• September: Elective in either FM (rural, community) or Peds (PICU/NICU if interested)
• October: Light elective (sports medicine, adolescent, or women’s health)
• November: Short FM/Peds outpatient block or interview buffer

At this point you should:

• Have 2 strong letters by early September: one FM, one Peds.
• Decide which field gets your primary push. You can dual apply if you are truly on the fence.

Track 3: “I am FM‑heavy, Med‑Peds as a stretch”

You do not need to contort your entire year for Med‑Peds, but you do need a genuine Med‑Peds exposure.

Recommended calendar:

• July: FM Sub‑I (home)
• August: Med‑Peds Sub‑I (away or home if available)
• September: FM elective (rural, academic, or underserved)
• October: Peds or IM elective (to round you out)

This track screams “future primary care doctor” to everyone. FM programs will be happy. Med‑Peds will see you as someone genuinely interested but not all‑in. That is fine if your main goal is matching FM.

Typical Number of Sub-Is by Specialty Interest

Category	Value
FM-primary applicants	2
Peds-primary applicants	2
Med-Peds-primary applicants	3

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Common mistakes with fourth‑year sub‑I scheduling

You are trying to avoid these. I have seen them sabotage otherwise solid candidacies.

1. Front‑loading random electives, pushing sub‑Is late

   • You do Derm, Cards consults, and Radiology in July–September.
   • Then your first Peds sub‑I is October.
   • By then, programs have already largely sorted their interview list.

2. Zero Med‑Peds exposure while applying Med‑Peds

   • “But I did IM and Peds cores!”
   • Med‑Peds wants to see that you sought out their environment. Residents, clinics, combined structure.

3. No outpatient FM exposure while selling yourself as primary care

   • Three inpatient months and no clinic.
   • Your story about loving continuity care sounds weak.

4. Step 2 scheduled during your most important sub‑I

   • Performance drops on both.
   • You get a vague letter and a mediocre score. Lose‑lose.

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Micro‑timeline: what to do each month as you move through MS4

To keep this practical, here is how your decision work shifts month by month.

April–May (end of MS3)

At this point you should:

• Finalize Step 2 date.
• Submit your school’s rotation requests with:
  • July–September anchored by 1–2 target sub‑Is.
  • At least one flexible elective month in fall.

June

• Finish MS3.
• Start dedicated Step 2 prep if testing soon.
• Email sub‑I directors for July/August to:
  • Confirm your spot.
  • Ask about expectations and how to earn a strong letter.

July–August

• Focus hard on:

  • Showing up early.
  • Owning your patients.
  • Communicating like an intern.

• Ask for letters in the last 3–5 days of the month:

  • In person, ideally.
  • With a short CV and personal blurb about your interests (FM vs Peds vs Med‑Peds).

September

• Double‑check:
  • ERAS is fully submitted.
  • Letters are marked “assigned” to your programs.
• If doing a sub‑I this month, repeat the “ask for a letter at the end” cycle.

October–January

• Prioritize:
  • Interviews over being a hero on service.
  • Rotations that align with your future field, but do not crush you.

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Quick comparison: how each specialty “reads” your calendar

Boil this down:

Field	What they like to see	Big red flag
FM	1 FM Sub-I, outpatient FM, community exposure	No FM sub-I at all
Peds	1 Peds Sub-I, maybe NICU/PICU, child-focused electives	Late or missing Peds Sub-I
Med-Peds	At least 1 Med-Peds Sub-I, IM + Peds depth	Zero direct Med-Peds exposure

If you can glance at your schedule and each column makes sense for that specialty, you are in good shape.

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Final checks before you lock the calendar

Before you hit “submit” on rotation requests, run this 7‑item checklist:

1. Do I have at least two sub‑Is scheduled, and do they cover the specialties I am serious about?
2. Is at least one sub‑I finished by end of August, latest September?
3. Is Step 2 not overlapping my most critical sub‑I?
4. Do I have meaningful exposure to:
   • FM clinic if applying FM.
   • Peds wards/clinic if applying Peds.
   • Med‑Peds service/clinic if applying Med‑Peds.
5. Do I have at least three faculty in mind who could write:
   • 1 in my top specialty.
   • 1 in a closely related field.
   • 1 department‑level or chair letter if needed.
6. Do I have one lighter month in Oct–Jan for interviews?
7. Would my calendar still make sense if I pivoted from, say, Med‑Peds to straight Peds?

If you cannot answer “yes” to most of these, shuffle months now. It is much easier than scrambling for letters in October.

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Key points

1. Anchor July–September with 2–3 targeted sub‑Is across FM, Peds, and Med‑Peds, based on your real priority order. Those months drive your letters and credibility.
2. Med‑Peds needs at least one explicit Med‑Peds rotation early; FM and Peds are more flexible but still expect one solid sub‑I each if you are seriously applying.
3. Protect Step 2, leave October–January lighter for interviews, and make sure your calendar tells a coherent story no matter which of the three you ultimately rank first.