First half-marathon: injury warning signs and a race-week checklist

In short: Cut your running by about half over the last two weeks but keep some faster running. Drink to thirst, not at every station: drinking far more than you sweat can cause dangerous hyponatraemia. See a doctor first if you get chest pain or faint on exercise. On race day, chest pain, collapse or confusion means the medical tent or 112.

India’s road-running season runs through the cooler months, and for many people this is the year of their first 21.1 km. The Vedanta Delhi Half Marathon was run on 18 October 2026. The Freshworks Chennai Marathon, which includes a half marathon, is on Sunday 3 January 2027, and the Tata Mumbai Marathon, which also has a half marathon category, is on Sunday 17 January 2027, according to the organisers. If you are entered for one of these or any other race this season, check the date, start time and route on the organiser’s own website.

This guide covers the last few weeks: how to taper, what to do in race week, how much to drink, the honest truth about heart risk, the aches that show up in knees and feet, and the red flags that mean stop. If you are still building up and your shins or ankles are the problem, our guide to HYROX training injuries covers shin splints, stress fractures, ankle sprains and safe build-up in detail, and most of it applies to running too.

Why first-timers get hurt more

New runners are injured more often than experienced ones. A meta-analysis of 13 studies in Sports Medicine found about 17.8 injuries per 1,000 hours of running in novice runners, against 7.7 in recreational runners. The last weeks before a race bring the biggest temptation to do too much: a missed long run, or panic that you are “not ready”.

The fix is not more training at the end. It is arriving at the start line fresh.

How should you taper in the last two weeks?

A taper is a planned cut in training before a race so your body can recover and absorb the work you have already done. A meta-analysis of 27 studies in competitive athletes, published in Medicine and Science in Sports and Exercise, found the best results came from a two-week taper in which training volume was cut by 41 to 60%, while intensity and the number of sessions stayed the same.

For a first half-marathon that means, roughly:

• Two weeks out: your last long run is done. Start cutting weekly distance so that, by race week, you are running roughly half of your peak week or less.
• Race week: shorter still. Keep your usual running days, with a few short efforts at race pace so your legs remember the rhythm.
• Do not cram. A missed long run cannot be made up in the last 10 days. Trying to do so is how people start a race already injured.
• No new strength or gym routines. Keep any strength work light and familiar.

The studies were in trained athletes, so treat the numbers as a guide. The principle, less volume but not zero intensity, holds for beginners too.

Your race-week checklist

Five to seven days before

• Confirm the start time, start-line location, bib collection and bag drop on the organiser’s site. Check the start time, as some races start very early.
• Plan transport so you arrive with time for the toilet queue.
• Shoes: race in a pair you have already run at least a few long runs in. Not new shoes from the race expo.
• Socks, shorts, top and sports bra: all worn before on a long run.
• Trim toenails a few days before, not the night before.
• If you take regular medicines, plan when you will take them on race morning. Ask your doctor in advance if you take insulin, blood pressure tablets or diuretics (“water tablets”), since a long run in the heat can change what you need.

The last two days

• Eat a bit more carbohydrate than usual (rice, roti, idli, poha, upma, bananas, curd rice) and a bit less fibre and fat if your stomach is sensitive. Nothing new.
• Drink normally. Your urine should be pale; there is no need to force extra water.
• Lay out kit the night before: bib with safety pins, shoes, socks, anti- chafe balm, cap, sunscreen, a small snack, and your phone with an emergency contact on the lock screen.
• Write any medical conditions, allergies and an emergency contact on the back of your bib if the organiser provides space.
• Sleep: the night before often goes badly. Two nights before matters more.

Race morning

• A familiar, light breakfast a few hours before the start, such as idli, toast with banana or poha.
• A small drink with breakfast, then sip to thirst.
• Apply anti-chafe balm and plasters to known hot spots.
• Start slower than you think. The first kilometres feel easy because you are rested and excited.

Drinking on the course: why more is not better

Indian races are often humid, and the instinct is to drink at every station. That instinct can be dangerous.

Exercise-associated hyponatraemia is a low blood sodium level that develops during or after endurance exercise. The 2015 international consensus statement, published in the British Journal of Sports Medicine, says it is caused mainly by drinking more fluid than you lose in sweat and urine. Severe cases cause swelling of the brain and can kill.

It is not rare. When researchers tested 488 runners at the finish of the 2002 Boston Marathon, 13% had hyponatraemia and 0.6% had a critically low level. It was linked to weight gain during the race, drinking more than 3 litres, drinking at every mile and finishing in over four hours. Slower runners are on the course for longer and pass more drinks stations, which is why first-timers need to know this.

What to do instead:

• Drink to thirst. The consensus statement calls this the safest individual strategy before, during and immediately after exercise.
• Know your sweat rate. The American College of Sports Medicine recommends weighing yourself before and after training to estimate it, and aims to keep sweat losses below 2% of body weight. If you weigh more after a long run than before, you drank too much.
• Sports drinks do not protect you if you overdrink. The consensus statement notes that sports drinks contain less sodium than blood, so they will not prevent hyponatraemia in someone drinking too much. They can still help with energy and with replacing some of the sodium lost in sweat in a long, sweaty run.
• Salt tablets are not a fix for overdrinking either. If you sweat heavily and leave salt stains on your cap, talk to a sports doctor or dietitian about a plan.

The warning signs of hyponatraemia overlap with heat illness: headache, nausea, vomiting, bloating, swollen hands, confusion, unusual behaviour and, in severe cases, seizures or collapse. Do not drink more water to treat these. Go to the medical tent and tell them how much you drank. The consensus statement says fluids by mouth or by drip should be withheld when hyponatraemia is suspected.

Heat illness on the course

Even a winter race in Chennai or Mumbai can be warm and humid by the time slower runners finish. Exertional heat stroke is a medical emergency. The American College of Sports Medicine’s 2021 consensus statement stresses that stopping exercise and rapid whole-body cooling are essential for survival: the longer the body stays severely overheated, the worse the outcome.

Slow down or walk if you feel dizzy, stop sweating, get a pounding headache or feel confused, and tell a marshal. Our guide to heat stroke first aid explains the signs and what to do in the first minutes.

Heart risk: rare, but know who should see a doctor first

Stories of runners collapsing make headlines, so it is worth getting the numbers right. A US study in the New England Journal of Medicine looked at 10.9 million runners in marathons and half-marathons over 10 years. There were 59 cardiac arrests, a rate of 0.27 per 100,000 participants in half-marathons, roughly one in 370,000, against 1.01 per 100,000 in full marathons. Men were affected far more often than women. The most common causes were hypertrophic cardiomyopathy, an inherited thickening of the heart muscle, and coronary artery disease. The authors concluded the overall risk is low.

The American College of Sports Medicine’s screening guidance says most people who are already active can keep exercising without tests, and that heart events during exercise are often preceded by warning signs. So the honest advice is not “everyone needs an ECG”, but see a doctor before race day if:

• you have had chest pain, pressure or tightness, unusual breathlessness, palpitations, dizziness or fainting during or just after exercise;
• you have known heart disease, high blood pressure that is not well controlled, diabetes or kidney disease;
• a close relative died suddenly and unexpectedly at a young age, or has an inherited heart condition such as cardiomyopathy. The NHS notes that most types of cardiomyopathy are inherited, and that hypertrophic cardiomyopathy is the most common cause of sudden unexpected death in young athletes;
• you have been inactive until recently and have any of the above. Your doctor can decide whether you need tests.

Never ignore chest pain because you are “fit”. Fitness lowers heart risk; it does not make it zero.

Knee, hip and foot pain in the last weeks

Pain around or behind the kneecap (patellofemoral pain, “runner’s knee”) often aches on stairs, squatting or after sitting. The 2016 international consensus in the British Journal of Sports Medicine recommends exercise therapy, and combined hip and knee strengthening rather than knee exercises alone.

Pain on the outside of the knee that comes on at a predictable point in a run is often called iliotibial band (ITB) syndrome. If it starts in race week, shorten your runs rather than pushing through, and see a doctor or physiotherapist if it keeps coming back.

Heel pain that is worst on your first steps in the morning suggests plantar fasciitis. The NHS advises rest, ice wrapped in a towel for up to 20 minutes every 2 to 3 hours, cushioned supportive shoes and gentle stretches, and seeing a doctor if it has not improved after 2 weeks of self-care.

See a doctor rather than race if knee pain comes with swelling, locking or giving way, if you cannot put weight on the leg, or if a pain is sharp, at one spot on a bone, or getting worse each run.

Blisters and chafing

These are small problems that can end a race. The NHS advises comfortable, well-fitting shoes broken in gradually, moisture-wicking socks, and not bursting a blister yourself: cover it with a soft or padded dressing instead. Anti-chafe balm or petroleum jelly on the inner thighs, underarms, bra line and nipples helps in humid weather. An infected blister, hot, red and with yellow or green pus, needs a doctor.

After the race

• Keep walking for a few minutes after the finish rather than stopping or lying down straight away, unless you feel unwell.
• Eat and drink to thirst. A meal with carbohydrate and protein, such as dal-rice, curd or eggs, within the next few hours. Do not keep drinking water by the litre to “flush out” the race.
• Expect soreness for a few days. Easy walking, gentle cycling or swimming are fine. Return to running when you can walk normally without pain.
• Pain that is getting worse, pain at one spot on a bone, or swelling after the race is not normal soreness. See a doctor.

Myths and facts

1. Myth: “You must carb-load for days before a half-marathon.”

Fact: Partly true. A review in Sports Medicine found that raising muscle glycogen above normal helps in events lasting more than 90 minutes but makes no difference in running lasting 60 to 90 minutes. Many first-timers take longer than 90 minutes, so eating more carbohydrate over the last day or two helps. A separate review suggests 30 to 60 grams of carbohydrate per hour during longer events. Carb-loading does not mean eating twice as much, and a huge meal the night before can upset your stomach.

2. Myth: “More water is always better.”

Fact: Drinking far more than you sweat dilutes your blood sodium. In the Boston study, drinking more than 3 litres and drinking at every mile were both linked to hyponatraemia. Drink to thirst.

3. Myth: “Sports drinks or salt tablets stop you getting hyponatraemia.”

Fact: Not if you overdrink. Sports drinks have less sodium than blood, and the consensus statement says they will not prevent hyponatraemia in a runner who drinks too much.

4. Myth: “Run through the pain; it is just your body adapting.”

Fact: Muscle tiredness and general soreness are normal. Sharp pain, pain at one spot on a bone, pain that changes how you run, and chest pain are not. Stopping costs you a race. Continuing can cost you months, or worse.

5. Myth: “If I am fit enough to run, my heart must be fine.”

Fact: The most common cause of race cardiac arrest in the US study was an inherited heart muscle condition that can be present in fit young people. Symptoms and family history matter more than fitness.

Red flags on race day: stop, get help

Stop and go to the medical tent, or ask a marshal to call for help, if you have:

• chest pain, pressure or tightness, or pain spreading to the arm, neck or jaw;
• sudden breathlessness, palpitations or feeling faint;
• confusion, slurred speech, unusual behaviour or a severe headache;
• vomiting, swollen hands and feet, or a bloated feeling after drinking a lot;
• you stop sweating, feel very hot, dizzy or unsteady;
• severe pain in a bone or joint, or you cannot put weight on a leg.

Call 112 at once if a runner:

• collapses, or is not responding normally;
• is not breathing normally: start chest compressions and send someone for an AED. In the US race study, bystander CPR was one of the strongest predictors of survival;
• has a seizure or is very confused after finishing.

The bottom line

Your first half-marathon is won in training, not in the last fortnight. Taper, arrive fresh, drink to thirst, wear what you have trained in, and start slowly. Heart events are rare, but chest pain or fainting on exercise, or a family history of sudden death, means seeing a doctor before race day. On the day itself, chest pain, collapse or confusion means the medical tent or 112, not the finish line.

Share this checklist with your running group.

This article is general health information, not medical advice. If you have symptoms or a medical condition, see a doctor before you race. In an emergency, call 112 or go to the nearest hospital.

Frequently asked questions

Do I need a heart check before my first half-marathon?

Most healthy people who already exercise regularly do not need tests before building up to a half-marathon, according to the American College of Sports Medicine's screening advice. See a doctor first if you have chest pain, unusual breathlessness, palpitations, dizziness or fainting with exercise, if you have known heart, kidney or metabolic disease such as diabetes, or if a close relative died suddenly and unexpectedly at a young age or has an inherited heart condition.

How much water should I drink during a half-marathon?

There is no single right amount, because sweat rates vary widely. The international consensus on exercise-associated hyponatraemia says the safest approach is to drink when you are thirsty. Do not force a cup down at every station. Weigh yourself before and after a long training run in similar weather: if you lost weight, drink a bit more next time; if you gained weight, you drank too much.

Should I carb-load before a half-marathon?

Partly. A review in Sports Medicine found that filling muscle glycogen above normal helps in events lasting more than 90 minutes but not in runs of 60 to 90 minutes. Many first-timers take longer than 90 minutes, so eating more rice, roti, idli, poha or bananas over the last day or two makes sense. That means more carbohydrate, not more food overall, and nothing new.

How long should I taper before race day?

For most runners, about two weeks. A meta-analysis of 27 studies in competitive athletes found the best results with a two-week taper in which training volume was cut by 41 to 60%, while intensity and the number of sessions stayed the same. In practice, run shorter, keep a few short faster efforts, and do not try to catch up on missed training.

What should I do if a runner collapses near me?

Shout for the nearest marshal or medical team and call 112. If the person is not responding and not breathing normally, start chest compressions straight away and keep going until help or a defibrillator (AED) arrives. In a US study of 59 race cardiac arrests, bystander CPR was one of the strongest predictors of survival.