Running with medication and heat: precautions you should know now

Heat and certain medications make a delicate combination for anyone who goes out for a run. When the temperature rises, the body is already working at the limit to dissipate heat through sweat, vasodilation, and a higher pulse; if, on top of that, there are drugs that promote dehydration, alter kidney function, or make thermoregulation harder, the safety margin narrows. On a long run, that effect can go from a simple discomfort to a serious problem.

The issue is not only what is taken, but when and in what context the run happens. Nonsteroidal anti-inflammatory drugs, some diuretics, several antihypertensives, certain antidepressants or antihistamines, and medications that increase sun sensitivity can completely change the equation on a muggy day. The most repeated risk is dehydration, but it is not the only one: there are also more cases of digestive irritation, kidney overload, dizziness, drops in blood pressure, and poorer tolerance to effort.

The body runs against the thermometer

During a run in the heat, the body behaves like an engine with the radiator at its limit. The hypothalamus acts as a thermostat, the skin receives more blood to release temperature, and sweat becomes the main cooling route. That mechanism is effective, but it comes at a price: water and salts are lost, heart rate rises, and the reserve available to sustain pace drops. In a race, every tenth of a degree counts.

Dehydration makes that scenario worse from the very first moment. You do not need to reach collapse to notice the effects: the stride feels heavier, perceived effort rises, the mouth dries out, and the head starts sending warning signs. If a drug promotes fluid loss, lowers blood pressure, or interferes with heat dissipation, the runner enters a risk zone much earlier than they imagine. Heat stops being just an environmental factor and becomes one more physiological load.

In competition, that thermal stress can amplify a problem that already exists at baseline. A person taking medication for blood pressure, an anti-inflammatory for a muscle ache, or an antihistamine for allergies does not respond the same as someone without that treatment. The difference may be noticeable in a summer 10K, but it becomes more evident in a half marathon, marathon, or long road sessions, where the body accumulates heat like a covered pot.

The drugs that make running in high temperatures more complicated

Among the medications that require the most attention are diuretics. Their function is to increase urine elimination, something useful in certain conditions, but not very compatible with running under the sun. If the body is already losing fluids through sweat, adding a medication that speeds up that loss can favor dizziness, cramps, drops in blood pressure, and a decrease in renal perfusion. Furosemide and some thiazides appear frequently in this risk group.

It is also worth looking closely at nonsteroidal anti-inflammatory drugs, known as NSAIDs. Ibuprofen, naproxen, and other drugs of this type can interfere with kidney function, especially when there is dehydration. The kidneys need prostaglandins to maintain their blood flow in situations of effort and heat; if that pathway is blocked, blood reaches the organ less effectively and the chance of acute kidney injury increases. In long races and in the heat, that combination is not theoretical: it has been observed in studies with ultrarunners and marathoners.

There are also medications whose effect changes when the body loses water. Some treatments for the heart, diabetes, epilepsy, or cholesterol can become more concentrated in the blood if hydration drops, with the resulting increase in adverse effects. There are also drugs that make it harder for the body to cool down normally, such as certain antidepressants, antipsychotics, first-generation antihistamines, Parkinson’s treatments, and some bronchodilators. The list is not meant to alarm, but it does mean understanding that the body does not process a gentle run in April the same way as a demanding race in the middle of August.

Photosensitizing medications add another layer of trouble. Some antibiotics, anti-inflammatories, diuretics, antihistamines, antidepressants, or acne treatments can increase the skin’s sensitivity to the sun. That means a greater chance of burns, redness, and irritation, something especially uncomfortable when training is done at midday or on a day of beach and asphalt. In a runner, exposed skin already takes enough punishment; if it also becomes more reactive, the risk clearly rises.

Ibuprofen and other painkillers are not a shield

Preventive use of ibuprofen before or during a race remains one of the most widespread and least justified practices. The idea that a painkiller will allow you to hold on for more kilometers has an intuitive logic, but scientific evidence has gone in the opposite direction. Pain does not disappear because the effort stops being harmful; only the signal that warns something is at its limit is reduced. In a long event, that can lead to running above the body’s real tolerance.

Digestive problems are among the best known. NSAIDs reduce the production of prostaglandins that protect the gastric mucosa, leaving the stomach and intestines more exposed to irritation, nausea, heartburn, diarrhea, or even bleeding. When you add the back-and-forth of exercise, the reduced blood flow to the viscera, and dehydration, the digestive tract becomes fragile ground. That is why so many runners describe the feeling that the stomach closes up, food comes back up, or cramps appear in the final stretch.

At the kidney level, the risk is even more delicate on hot days. Running redirects blood toward the muscles and the skin, just when the kidneys need to keep filtering normally. If you also take an anti-inflammatory, that perfusion can be reduced even more. In practice, the runner is left in a kind of uncomfortable triangle between sweat, effort, and medication. The consequence can range from a slight temporary alteration to acute kidney damage, especially in prolonged efforts and under intense heat.

Paracetamol is not an automatic solution for running without consequences either. Although it does not act as an anti-inflammatory and usually irritates the stomach less than an NSAID, it is still a drug and not a harmless shortcut. Its use should respond to a specific indication, not to the idea of masking discomfort in order to complete training sessions or races. In endurance sport, the great temptation is to confuse relief with recovery, and they are not the same. The first may last an hour; the second demands respect for the physiological process.

What the evidence shows in long races

The available research agrees on one essential point: taking anti-inflammatories preventively does not reliably improve performance and can increase adverse effects. Studies in marathon and half-marathon runners have observed more gastrointestinal discomfort, more complaints of post-race pain, and, in some cases, more kidney problems in those who used painkillers before or during the event. The idea of performance protected by a pill does not hold up well when compared with the data.

In ultradistance, the warning sign is even more obvious. The longer the event, the more time the body spends in progressive dehydration, the digestive system in hypoperfusion, and the kidneys in a state of stress. That is why some competitions have restricted the use of ibuprofen during the race. This is not a paternalistic gesture, but a practical reading of the risk: the longer the effort lasts, the less room there is to pay for medication mistakes.

There is also evidence that removing pain does not mean reducing real damage. Some people feel subjective improvement with an anti-inflammatory and believe they have solved the problem, but the tissue may still be injured or in repair. Inflammation, with all its nuances, is not always an enemy; often it is part of the recovery mechanism. Blocking it indiscriminately can interfere with the normal healing of muscles, tendons, and bone, especially if the sports load is not adapted to the underlying problem.

The journalistic lesson is uncomfortable but clear. Frequent use of painkillers in runners is not supported by a solid basis for improving performance and is linked to more risks, especially when it coincides with heat, dehydration, and prolonged efforts. The culture of endurance has a bright side in competition, but a dull one when it becomes a pharmacological habit.

Warning signs that should not be normalized

On a run in high temperatures, there are symptoms that require slowing down or stopping. Persistent dizziness, confusion, chills in warm weather, intense headache, nausea, vomiting, absence of sweat despite effort, unusual palpitations, or a feeling of weakness that does not go away are relevant signs. If, in addition, the person has taken medication that can alter hydration or kidney function, caution should be greater.

Digestive discomfort should also not be treated as a race anecdote. An upset stomach after taking an anti-inflammatory before running is not a minor toll, but a clue that the body is protesting. If the runner has also drunk too much in a short time, sodium balance can be altered and hyponatremia may appear, a rare but potentially serious complication. The mix of heat, water, effort, and drugs does not always behave the way the person pinning on a bib expects.

The skin also speaks. Unexpected burns, spots, itching, or marked redness after training outdoors may point to drug-induced photosensitivity. In summer, that detail matters as much as average pace. A runner with irritated skin loses comfort, but also part of their ability to keep training normally in the following days. The problem does not end with the session; sometimes it starts there.

Real prevention starts before tying your shoes

The safest way to face a race in the heat is to arrive with medication reviewed and the body well hydrated. That does not mean stopping treatments on your own, but understanding that some drugs require more attention in summer. In particular, medications for blood pressure, diuretics, NSAIDs, and those that interfere with sweating or the sensation of thirst deserve a careful reading of the leaflet and professional advice when there are doubts.

Training time also matters a great deal. Running early in the morning, looking for shaded areas, reducing exposure on extreme days, and adjusting the duration of the session are simple decisions that change the risk. A race at 22 degrees and moderate humidity does not behave the same as a run at midday with 35 degrees and a higher heat index. The body does not negotiate with the mercury; it obeys it or breaks.

Hydration should be understood as a continuous strategy, not a last-minute rescue. Drinking regularly before, during, and after effort helps maintain blood volume and protect kidney function. But it is also not wise to fall into the trap of too much water without salts, because the body needs balance. In long events, sodium and fluid replacement should be reasonable and adjusted to actual sweating, not to an abstract idea of drinking more as a rule.

Clothing, the simplest gesture, also matters. Lightweight, breathable, light-colored fabrics help dissipate heat and reduce sun exposure. In runners taking photosensitizing medications, sun protection and covering the skin stop being an optional recommendation. They are part of basic safety, just like not going out with a broken shoe or a poorly adjusted heart-rate monitor.

A running summer demands less improvisation and more judgment

The image of the runner who solves a discomfort with a pill before the start is still very common, but summer makes it especially fragile. Heat adds an invisible pressure that multiplies the risks of several common medications. What on a cool day might go unnoticed becomes, with high temperatures, a factor that can alter everything from sweating to kidney work. Running, then, no longer depends only on legs and lungs.

The useful message is simple and severe at the same time: medication does not adapt to the desire to compete. It adapts to each person’s health status, their treatment, and the context they are in. In summer, that context is more demanding, drier, and less forgiving of excess. Prudence does not take away sporting merit; it prevents a bad calculation from ruining weeks of training or, worse, ending in a medical emergency.

There is one underlying idea worth keeping in mind. Pain, thirst, fatigue, and heat are not capricious enemies: they are messengers. Silencing them without judgment can make the race quieter, yes, but also more dangerous. And when the asphalt is burning, that difference between ignoring a signal and respecting it can mark the line between finishing with confidence or paying for the start long after crossing the finish line.