Behind on Marathon Training? How to Get Back on Track and When to Defer
Updated: Oct 16
Written by Andy Hood · Ultra runner, cancer survivor and Runna ambassador
Updated 16 October 2026 | First published 7 August 2026
Article contains affiliate links/codes that support this blog and my cancer charity work.
Fallen behind on your marathon training? Here's how to rebuild your long run, what to cut first, when to change your goal or defer, and how I'm rebuilding for London 2027 after emergency surgery.
You open your training app on Sunday morning. The plan says 14 miles. Your watch says the longest thing you've run in three weeks was a sprint for the bus. Somewhere between the cold that went round the office, the niggle that turned into a fortnight off and the deadline that ate your evenings, the plan and the training parted ways. And race day hasn't moved an inch.
I know that feeling better than most. In April I was lying in a hospital bed after emergency surgery, my race calendar in pieces and yet another organ lighter. By my maths that should make me faster. The evidence is still pending. Five years earlier, testicular cancer took my running shoes away for months. Both times I came back, and both times I learned the same lesson: a derailed build is not a dead one.
The quick answer on falling behind with marathon training: If you've missed one to three weeks, you can almost certainly still run your race. Don't try to make the missed runs up. Restart from your longest run of the last three to four weeks, rebuild the long run by one to two miles a week, keep the easy miles, drop some speed work, and revise your goal time if you've lost more than about ten days in the final eight weeks.
Behind on marathon training at a glance:
Missed up to a week: carry on with the plan. Don't make anything up.
Missed two to three weeks: rebuild from your longest run of the last month, not from the plan.
Long run: add one to two miles a week, longest run two to three weeks before race day.
What to cut first: fast intervals, never the easy miles.
Goal time: revise it if you've lost 10+ days in the final eight weeks.
Golden rule: never cram missed miles.
I'm not a qualified running coach or medical professional. This is what I've learned across many training blocks and two comebacks. If you're injured or unwell, speak to a physio or your GP first.
This is part of my Road to London Marathon 2027 series. Not behind yet and just want to know when to start? My London Marathon 2027 training plan has the dates. This one's for when the plan has already gone sideways.
Contents
Can You Still Run a Marathon If You've Missed Training?
Usually, yes. Put the panic down for a minute.
The bad news first: you can't cram a marathon build. The missed miles are gone, and squeezing them into the weeks that remain is the single most reliable way to arrive at the start line injured, or not arrive at all. Every coach will tell you the same, so let's not pretend otherwise.
Now the good news. Fitness fades far more slowly than panic suggests. A few days or even a week off barely dents an aerobic base you've spent months building, and measurable fitness loss generally takes two to four weeks of complete rest, according to RunnersConnect. If you were running consistently before life got in the way, most of that work is still in the bank.
What decides your race now isn't what you missed. It's what you do with the weeks you have left.
How Far Behind on Marathon Training Are You?
Before you change anything, pin down two numbers.
1. Weeks to race day. Count them properly, and remember the last two to three are taper. Ten weeks out gives you roughly seven or eight weeks of real training.
2. Your longest recent run. Not your longest ever. Your longest in the last three to four weeks. The 20 miler you ran three years ago doesn't count, however fondly you remember it. That recent number, not the plan you set up on day one, is your true starting point.
A rescue plan built from where you actually are will beat a heroic plan built from where you wish you were, every single time.
Spring 2027 Marathon Dates and When Training Should Start
Here's where the big spring 2027 marathons fall, and when week 1 of a typical 16-week plan would have started. If you've only just begun and today is well past that date, you're behind. Welcome to the club, it's a big one.
Race | 2027 date | Week 1 of a 16-week plan |
Tokyo Marathon | Sun 7 March | Mon 16 Nov 2026 |
Brighton Marathon | Sun 4 April | Mon 14 Dec 2026 |
Paris Marathon | Sun 11 April | Mon 21 Dec 2026 |
Manchester Marathon | Sun 18 April | Mon 28 Dec 2026 |
Boston Marathon | Mon 19 April | Mon 28 Dec 2026 |
London Marathon (The Double) | Sat 24 or Sun 25 April | Mon 4 Jan 2027 |
Notice how many of those plans start right on top of Christmas. That's not a coincidence, that's why so many of us are behind by February.
Running Brighton or Manchester? I've covered both courses in my Brighton and Manchester training plans guide. Chasing a Major star? See my Abbott World Marathon Majors guide.
What to Do If You've Missed Weeks of Marathon Training
If you've missed weeks of marathon training, step back in your plan rather than jumping ahead, rebuild the long run from where you are now, and match your goal to the time you have left. Find your row and your column. The more you've missed and the less time you have, the more your goal should shift from a time to a strong finish.
Training missed | 10+ weeks to race | 6–9 weeks to race | Under 6 weeks to race |
A few runs, up to 1 week | Carry on with the plan. Don't make anything up. | Carry on. Protect the next long run. | Carry on. Trust the taper. |
2–3 weeks | Step back one or two weeks in the plan; trim later, not the taper. | Rebuild the long run from your current longest. Expect to adjust your goal slightly. | Run for a strong finish. Keep long runs modest. |
4+ weeks | Treat it as a fresh, shorter build. Your goal time likely moves. | Run for the finish, or look at deferring. | Seriously consider deferring. |
Essentially starting again but with plenty of time? My full 20-week marathon plan shows the shape of a complete build.
How to Catch Up on Marathon Training Safely: 6 Rules
To catch up on marathon training safely, don't add the missed miles back. Protect the long run, cut speed before volume and stay consistent. With your real starting point in hand, the priorities are ruthless and simple.
1. Protect the long run above everything. If you can only keep one session a week, this is it. Build it by one to two miles a week from your current longest, with an easier week every third or fourth. Aim to hit your longest run, somewhere between 16 and 20 miles depending on where you started, two to three weeks before race day.
2. Don't make up missed runs. Doubling up to "catch up" piles stress on a body that's just had less. It wears the disguise of dedication and it's how good blocks unravel. Pick the plan up from where your fitness actually is.
3. Know which sessions matter most. In order: the long run, then one quality session (tempo or marathon-pace work), then easy miles. Fast intervals are the first to go.
4. Drop intensity before volume. It's the steady aerobic miles that carry you through mile 20. Since my surgery I've run almost all my easy miles in Zone 2, and my heart rate at easy pace has improved more than in any block before it. Running slower makes you a better runner, who knew? My Zone 2 running guide explains how.
5. Consistency beats heroics. Five modest, repeatable weeks will do far more for your race than one massive week followed by a breakdown. If it's a choice between an extra session and finishing the week healthy, finish the week healthy.
6. Sleep, strength and fuelling are training too. A body coming back from disruption adapts through recovery. Keep two short strength sessions a week. Calf raises, lunges, squats and hip thrusts with my strength coach Steve carried me back this year, bongos and all. And practise your race fuelling on every long run; my guide to carbs per hour covers the numbers.
Rebuilding Your Long Run When You're Behind on Marathon Training
Rebuild your long run gradually from your current longest, not from where the plan says you should be. Add a little each week, build in easier weeks, and aim to have your longest run done two to three weeks before race day, leaving time for the taper.
You won't find a week-by-week table here, and that's deliberate. A plan copied off the internet, or knocked up in a chatbot in thirty seconds, doesn't know your running history, can't see how last Sunday went, and won't notice when your calf starts grumbling.
When you're already behind, that's exactly when you need a plan that's watching. I've explained why in ChatGPT vs Runna: why a chatbot isn't a running coach.
What matters is the principle: build from where you are, and if any long run leaves you wiped out for days, repeat that week rather than pushing on. Nobody hands out medals for week 6.
Returning to Marathon Training After Illness or Injury
After illness, come back at easy effort before adding any intensity. After injury or surgery, get the all-clear first and let the injury set the pace. How you lost the weeks matters as much as how many you lost.
Running After Illness
If you missed training through illness, make your first week back the same amount of running time as before, all at easy effort. Add intensity only once easy runs feel normal again. And please, don't run with a fever or chest symptoms. The marathon will still be there next week. So, hopefully, will you.
Running After Injury or Surgery
If you missed training through injury or surgery, get a physio's or your doctor's go-ahead first. Then the injury sets the pace, not the calendar. Rebuild easy running before the long run, and treat any pain that changes your stride as a stop sign.
After my surgery I kept my easy runs on the flat for weeks before going back to the hills, kept up strength training and a monthly massage, and dialled my hill reps back from an RPE of 9 to 10 to a controlled 7 to 8. Running to feel rather than pace is a big help here; my guide to running to RPE in Runna explains how. If long runs keep aggravating things, read the next section.
When to Change Your Marathon Goal Time or Defer
Here's the conversation nobody enjoys. If you've lost more than about ten days of training in the final eight weeks, your goal time probably needs to move. Human Kinetics' marathon coaching guidance uses the same threshold.
That's not failure, it's course correction. A marathon run well at a realistic pace beats a blow-up chasing a number your training no longer supports, and finishing strong sets you up for the next build. Some of my favourite races have been the ones where the time goal quietly left the building.
And sometimes the right call is the hardest one. If long runs keep aggravating an injury, or the maths simply doesn't work, look at deferring. Check the race organiser's website for their deferral terms and conditions early, because deadlines come round faster than long runs do.
London Marathon 2027 Deferral Rules
Because the 2027 TCS London Marathon runs over two days, the deferral rules depend on your day. Sunday ballot runners who defer get a 2028 place. Saturday runners are offered a Sunday place in 2028, 2029 or 2030 at the organisers' discretion.
Charity runners defer through their charity, not the race, and a deferred place still means paying a future entry fee. Whichever marathon you've entered, check the race organiser's website for their terms and conditions, because deferral rules and deadlines differ from race to race.
My London Marathon 2027 Comeback After Surgery
In 2021 testicular cancer took running away for months. Before that I was a 3:45 marathon runner, nothing to shout about, ticking along. I rebuilt with Runna and my marathon came down to around 3:20. Not because I ran more miles, but because every mile finally had a purpose.
Then April 2026, and a second rebuild I never saw coming. This time I followed every rule in this article:
A recovery programme with the weeks out of my shoes built in.
Then Run to Maintain, with easy miles on the flat.
Strength twice a week and a monthly massage.
No chasing old paces, however much they taunted me from the app.
When I was lying in hospital in April, a 5-mile time trial felt a very long way away. In early autumn Runna set me one with a 7:50/mile target. I ran it at 6:50 to 7:00, with the app telling me to slow down the whole way. I did, mostly. A progressive half-marathon long run followed, and next up is the Krispy Kreme London 50 on 7 November: 50K across London, visiting 20 Krispy Kreme shops and fundraising for cancer charity ChemoHero.
After that comes the 2027 TCS London Marathon on Sunday 25 April, running for The Robin Cancer Trust dressed as a giant pair of testicles. I'll be very hard to miss. After the London 50 I drop back to a maintenance plan, then my 16-week London block starts the week of 4 January.
Does Runna Adjust Your Plan If You Miss Training?
Yes, and that's exactly what made my compressed rebuild work. Runna assesses every run against its targets, tells you whether you're on, ahead or behind, and adjusts what comes next. You can drag sessions around when life explodes, flag that you're not feeling 100%, or switch on holiday mode. When surgery took me out, it rebuilt the plan around the time I'd lost. For runners with a base and a late place, there's also a 12-week fast-track marathon plan. My Runna training plans explained guide covers each one.
Now, where it falls short, and I say this as a fan. Runna can rebuild your plan around an injury, but it can't look at one. It isn't a physio and it isn't free. If something hurts, get it checked before you let any app, Runna included, build you back up. And if budget is the deciding factor and you own a Garmin, Garmin Coach is a free alternative worth a look.
Whatever you train with, make sure the plan starts from the runner you are today, sees how each run went and changes when you do. That rules out anything printed off the internet. If you'd like a plan that does all of that, start a free Runna trial with code ANDY2 and get 14 days instead of the usual 7.
How to Get Back on Track With Marathon Training: My Summary
First, face the numbers. Weeks to race day and your longest run of the last month. That's your plan now, not the one you set up on day one.
Secondly, protect the long run and stop chasing the missed miles. Build steadily, keep the easy running, and let the speed work go first.
Thirdly, be brave enough to change the goal. A revised time or a deferred place isn't failure. Arriving broken is.
Get this right and you'll arrive at the start line trained for the race you can actually run, rather than the one you planned when race day felt a lifetime away.
Lace up, enjoy your miles.
Behind, but not beaten. See you at the start line.
Behind on Marathon Training FAQs
Can I still run my marathon after missing 3 or 4 weeks of training?
Usually, yes, if you had a solid base before the gap. Restart below where you left off, rebuild the long run gradually and revise your goal time realistically. With under six weeks to go, run for the finish or consider deferring.
Should I make up missed marathon training runs?
No. For a few missed runs, carry on with the plan as written. Cramming extra miles into the following days raises injury risk more than the missed runs cost you.
Is 8 weeks enough to train for a marathon?
Eight weeks is enough to rescue a build that already has a base, giving about six training weeks plus a two-week taper. It isn't enough to train from scratch. Your longest run in the last month tells you which situation you're in.
Is 12 weeks enough to train for a marathon?
It is if you already run regularly and have done a half marathon. Twelve weeks allows a gradual long-run build to 18 to 20 miles plus a taper. First-time marathoners starting from little running should allow 16 to 20 weeks.
What should I prioritise if I'm behind on marathon training?
The weekly long run, built from your current fitness. Then one quality session, then easy aerobic miles. Fast intervals go first.
How long should my longest run be if I'm behind?
Aim for 16 to 20 miles two to three weeks before race day, reached by adding one to two miles a week. If you can't get there safely, a longest run of 14 to 16 miles will still get most people round with a revised goal.
Should I still taper if I've missed training?
Yes. Skipping the taper trades a small, uncertain gain for a tired start line. Keep at least the final two weeks of reduced volume. My guide to surviving the taper explains why it feels so hard.
When should I defer a marathon instead of running it?
Defer when long runs aggravate an injury, or when your longest recent run makes the maths impossible even with a revised goal. Check the race organiser's terms and conditions early, because deferral rules and deadlines differ from race to race.
Exclusive Runna Premium trial offer: click to access, or download the app and use code ANDY2.
This article is based on my own experience and published coaching guidance. It isn't medical advice. If you're injured, unwell or returning from surgery, talk to a physio or your GP before you start building back up.
About the Author - Andy Hood
About the author: Andy Hood is an ultra and endurance runner, cancer survivor, unapologetic advocate for men's health and Runna Ambassador.
Diagnosed with testicular cancer in 2021 after a timely prompt from Jeremy Clarkson to check, he now runs to support others in the fight, raising over £28,000 for cancer charities through self-designed challenges like the Krispy Kreme London 50.
Based in North Devon, he trains on the Tarka Trail, heads to Chamonix for UTMB week most years, and will run the 2027 London Marathon for The Robin Cancer Trust dressed as a giant pair of testicles.
Follow his runs, read his race reports, and grab a pair of Check Ya Balls at runningwestwardho.co.uk.
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