How to run a half marathon after 40

A half marathon is 21.1 kilometres, or 13.1 miles. It is the first distance where running stops being purely a question of endurance and becomes a question of planning. You can get through 10K on stubbornness and three runs a week. A half marathon asks you to decide in advance how you will handle the second hour: what you put into your stomach, how fast you set off, and what you do in the final weeks before.

The good news is that the step up is longer without being harder. You are mostly doing the same thing you did on the way to 10K, for more weeks. This guide spends most of its time on the three variables that are genuinely new, because that is where most first half marathons come unstuck.

Before you start: are you at the right starting point?

The plan below assumes a specific level. Start below it and the middle weeks will be too heavy, and then things end the way they usually end.

• You can run 10K continuously at an easy pace and you are not wrecked afterwards. Perfect. The plan is built for exactly you.
• You can cover 10K, but only with walk breaks or by really digging in. Stay at that level for another three or four weeks without increasing anything. Come back here when 10K feels routine rather than like an achievement.
• You are not at 10K yet. Start there instead. The whole route is in the guide on how to run 10K, which also owns the research on how quickly a body can safely take on more. If 5K is the current target, there is a plan for 5K. If you are completely new to running, start with walk and jog intervals in the running guide for over 40s.

If you have twelve weeks until a race you have already entered but you are honestly on the second bullet, pick a later race rather than a harder plan. Sixteen weeks from a shaky 10K is a better deal than twelve weeks from a 10K you do not really own.

What is actually new compared with 10K

This is the whole reason a half marathon plan looks different rather than simply longer.

1. The long run passes an hour. That is when your body's stored fuel starts running down in a way it does not on shorter runs. It is the one point in this guide where you have to learn something genuinely new, namely eating while you run.
2. The week gets big enough to demand real rest. On the way to 10K you can get away with simply pressing on. Here you cannot. Every fourth week needs to be noticeably lighter, not just slightly lighter.
3. The last two weeks are when you train less. That feels wrong, and it is the most common deviation I see in people training on their own. The taper is not lost time. It is one of the best-evidenced parts of the plan.

The long run: count minutes, not kilometres

Nearly every plan online measures the long run in distance. That is the wrong unit here, for a simple reason: your body does not register kilometres, it registers time under load. A 14 km long run is a completely different session for someone running 6:00 per km than for someone running 8:00. The first is out for 84 minutes, the second for 112. Same number in the plan, half an hour of difference in actual load.

So the table below is written in minutes. Run it at the easy pace where you could hold a conversation, the effort described in the guide on zone 2. The kilometres arrive on their own.

How much can it grow?

The rule is the same one that built your 10K, so I will not repeat it here. What drives the risk is the size of the jump in your longest single run compared with recent weeks, not how much your weekly total goes up. The full case for that, with the studies behind it, sits in the 10K guide. The plan below is built to satisfy that rule: the long run grows by ten to fifteen minutes at a time, and every fourth week it drops back sharply.

Where the long run should stop growing

Around two hours. Get there and you have built what you need to cover 21 kilometres, whether two hours takes you 15 km or 19 km. Pushing beyond that costs more recovery than it gives back, and recovery is the scarce resource when you are over 40 with a job and a family.

Do you need a fourth run?

No. Three runs a week builds a half marathon, and the plan below is built on three. But this is the first distance where a fourth run is a genuinely reasonable option, so it deserves an honest answer.

A fourth run helps only if it stays short and easy. Thirty to forty minutes at the same soporific pace as the long run. The point is to give your body more chances to get used to running, not more load. Run the fourth one hard and all you get is a fourth chance to be tired.

But here is the trade that actually matters: if you have forty spare minutes a week, most comeback bodies get more out of putting them into strength training than into a fourth run. Strong hips and calves are what hold the middle weeks of this plan together. The session and the progression are in the guide on strength training at home. Keep the two strength sessions you already do through the whole plan. How to place them against your runs without one dragging the other down is covered in the guide on strength training and running. They should get shorter during the taper, not disappear in week three.

As for the faster session: one a week, at most. If you want intensity control, session types and a ladder to climb, it is all in the guide on running intervals. Within this plan the fast run is a garnish, not the main course. The long run is the main course.

The 12-week plan

Three runs a week. One long run that grows, two short ones that mostly stay put. Everything easy except what is explicitly marked as faster.

One small but important choice in that table: the two short runs barely grow. That is deliberate. If something is going to increase, it should be the long run, because that is where the adaptation towards 21 km lives. Letting all three runs grow at once is the most common route to being exhausted by week six.

If you have to choose between running a hard session on tired legs and moving it, move it. If you would rather base that decision on something measurable than on a guess, the guide on HRV and daily readiness explains how to read your morning number and what to do with it. The rule there is to change the intensity, not to skip the run.

Food and drink once a run passes an hour

This is the only genuinely new skill in the guide, and the one most people put off until race day punishes them for it.

Why it is needed

Your body stores a limited amount of carbohydrate. On shorter runs that store is plenty. Once the work stretches out over time, taking fuel on board during the run becomes a performance factor rather than a detail. For exercise lasting longer than about an hour, the joint position stand from the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine recommends 30 to 60 grams of carbohydrate per hour.

How many grams each serving gives you is on the packaging, and it varies between products. A sports gel usually holds around 20 to 25 grams, half a litre of sports drink around 30. For a half marathon taking two to three hours, the recommendation works out at roughly 60 to 180 grams in total, spread evenly across the race. Do the sums on whatever you actually plan to use. For a run under an hour you need none of this, and water is enough.

How to practise it

1. From week 5 take something to eat on the long run. Try one product at a time.
2. Eat earlier than you think you need to. Around forty minutes in, then every thirty to forty-five minutes. Waiting until you feel empty is waiting too long.
3. Week 9 is the dress rehearsal. Use the exact product, the exact amount and the exact timing you intend to use in the race.
4. Never try anything new on race day. Not a new gel, not the organiser's sports drink unless you know which one it is, not a new breakfast. Your stomach is the most common reason a well-prepared half marathon still turns into a miserable one.

Breakfast beforehand: something you already know you tolerate, two to three hours ahead. What your body rebuilds itself with between runs is a separate question. That one lives in the guide on protein after 40.

Drinking: let thirst decide

Current guidance for endurance running is to drink to thirst. That sounds banal, but it is the conclusion drawn from the fact that both extremes are worse. Drinking too little hurts performance. Drinking more than thirst calls for is the most common cause of exercise-associated hyponatraemia, a dangerously low sodium concentration in the blood, which is rare but serious in long races.

The taper: those final two weeks

If you take only one thing from this guide, take this. Tapering is one of the best-evidenced parts of a training plan, and it is also the thing people choose to ignore, because training less feels wrong just as the race approaches.

A meta-analysis by Bosquet and colleagues from 2007 pulled together what actually works. The most effective strategy was two weeks in which training volume is reduced by between 41 and 60 per cent, while intensity and the number of sessions are left unchanged. So: shorter runs, just as many of them, at the same speed as before. Not fewer runs, and not easier ones.

A systematic review with meta-analysis published in PLOS One in 2023, pooling fourteen studies, points the same way on performance: both time-trial results and time to exhaustion improved after a taper. But the same review found no improvement in maximal oxygen uptake or in economy of movement. Its studies covered endurance athletes across several sports, not runners alone.

That is worth pausing on, because it tells you what a taper actually does. It does not make you stronger or fitter. The engine is unchanged. What changes is that you arrive at the start line rested instead of tired, and that is enough to transform how the whole race feels. You built your fitness in weeks one to ten. The last two weeks are only about not spoiling it.

In practice: keep the fartlek in week 11, just make it shorter. Shorten the strength sessions but keep them. Resist the urge to add one last long run to check that you can manage the distance. That run builds no new fitness. It simply spends what you were going to use on race day.

Race day: pace decides everything

A half marathon is long enough to punish an overly fast start properly. The first few kilometres always feel easy, and that is exactly where the mistake gets made. Adrenaline, other runners and rested legs conspire to nudge your pace up by ten to twenty seconds per kilometre without it registering.

• Set off slower than you want to. Aim for the pace you have been running your long runs at, not faster. If the first 5K feels almost too easy, you have got it right.
• Split the race into thirds. First seven kilometres: hold back. Middle seven: sit there. Final seven: this is where you spend whatever is left.
• Eat to the schedule, not to how you feel. The same timing you rehearsed. By the time you feel empty it is too late to fix.
• Expect it to get hard around kilometre 15 to 17. That is normal, not a sign that something has gone wrong. It usually eases.

How long it takes

A half marathon is 21.1 km, or 13.1 miles. The table is straightforward arithmetic on your pace, not a prediction for you.

For someone who has just built up to the distance, a first half marathon usually lands between two and three hours. Aim to finish in control rather than to hit a time. The time comes next time, for free, from the fact that you are still running.

When to stop training and contact a doctor

• Call emergency services immediately (911 in the US, 999 in the UK, 112 across the EU): severe or crushing chest pain that does not ease within a few minutes of rest, especially alongside breathlessness, nausea, cold sweats or feeling faint.
• Contact a doctor promptly: pressure or pain in the chest that returns every time you exert yourself and eases when you rest. That can be angina and should be investigated, not trained through. The same goes for new breathlessness out of proportion to the effort, or an irregular heartbeat.
• Do not train with an infection. A fever or an active infection is a reason to rest, not to push on with the plan. A couple of missed runs in week seven costs nothing. One hard run with a fever can cost a great deal.
• Book a physiotherapist: pain that makes you limp, that persists at rest, that wakes you at night or that gets worse with every run. Pinpoint pain along the shin that worsens over weeks should be taken seriously and not trained through.
• Carry on gently: general muscle soreness that fades within a couple of days is normal adaptation.

This is general health information, not a diagnosis or personal medical advice. If you are unsure, contact your doctor or a nurse advice line.

After the race

Two weeks of very little. Walk, cycle gently, run short if it feels good. Your body has just done something it had not done before, and that takes longer to recover from than the tiredness itself suggests. Sleep is the most important part of that work, and it is covered in the guide on sleeping better after 40.

Then pick one thing. Not three.

• Keep the distance. One 90-minute long run a week, two short ones. That holds you at half marathon level more or less all year, for fairly little outlay.
• Get faster over the distance. The same weeks, with one structured faster session a week, following the ladder in the intervals guide.
• Build further. If you want to go longer, the principle is the same again, over more weeks. But do not do it straight after your first half marathon. Give tendons and bone six months at this level first.

Chasing longer and faster at the same time is the most common route back to square one. That holds exactly as true here as it did at 10K.

Frequently asked questions

How long does it take to train for a half marathon?

If you can already run 10K continuously, twelve weeks of three runs a week is enough for most people. Coming from a lower base, sixteen weeks is a better starting point than twelve. What decides the outcome is how consistently you run, not how old you are. If you need to slot in an extra easy week along the way, the result is worth exactly as much.

Do I need to run the full 21 km in training first?

No. Once your longest run reaches roughly two hours of continuous running, you have built what you need. Race day takes care of the final few kilometres. Running the whole distance in training costs more recovery than it returns, especially for a body over 40 that already has plenty to deal with.

How long does it take to run a half marathon?

A half marathon is 21.1 km, or 13.1 miles. At a pace of 6:00 per km (9:39 per mile) it takes 2 hours 7 minutes. At 7:00 per km (11:16 per mile) it takes 2 hours 28 minutes, and at 8:00 per km (12:52 per mile) it takes 2 hours 49 minutes. For someone who has just built up to the distance, a first half marathon usually lands between two and three hours. Every one of those times is entirely normal.

Do I need to eat during a half marathon?

Yes, for most people. For exercise lasting longer than about an hour, the guidance is 30 to 60 grams of carbohydrate per hour, which in practice means a gel or a sports drink every thirty to forty-five minutes. Under an hour you need nothing at all. The important part is practising exactly what you plan to use on several long runs first. Race day is the wrong day to try something new on your stomach.

How many runs a week do I need?

Three runs a week will build a half marathon, and that is what the plan here is based on. A fourth run is the first genuinely sensible option if you want more, but only if it stays short and easy. If you would rather put that time into strength training, that is the better trade for most comeback bodies.

Sources for the figures in this article: Thomas, Erdman & Burke, joint position stand of the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine, Medicine & Science in Sports & Exercise 2016 (carbohydrate during exercise lasting longer than an hour); Bosquet et al., meta-analysis on tapering, Medicine & Science in Sports & Exercise 2007 (two weeks, volume reduced 41 to 60 per cent, intensity and frequency unchanged); Wang et al., systematic review with meta-analysis of fourteen studies, PLOS One 2023 (performance improved, oxygen uptake and economy of movement unchanged); NHS guidance on chest pain and on exercising with an infection; the collected literature on exercise-associated hyponatraemia (drinking to thirst, overdrinking as the main cause). The progression research behind the plan's rate of increase is set out in the 10K guide.