Heat, Hydration, & Your Health

If you have stepped outside in Indiana this summer, you already know. The air is thick, the pavement is hot, and the "feels like" temperature has been reading higher than the actual number for weeks. Central Indiana just came off an extreme heat warning stretch with heat indices between 105 and 110 degrees, and the forecast is not offering a graceful exit anytime soon.

In my practice, I have watched what this kind of heat does to otherwise healthy people. Headaches by lunchtime. That flat, foggy feeling in the afternoon. A "why am I so tired?" that has nothing to do with sleep. Almost every time, the fix is not more caffeine, more supplements, or a new gadget. It is water. Boring, unglamorous, and one of the most powerful medical tools you already own.

Today I want to walk you through what heat actually does to your body, why hydration is a bigger deal than most people realize, and the simplest ways to stay well through the rest of an Indiana summer.

Your body is roughly 60% water, and it uses that water for almost everything that keeps you alive. Water carries nutrients to your cells, flushes waste through your kidneys, cushions your joints, and, critically in a summer like this one, regulates your temperature through sweat.

When you get low on fluids, none of those systems work as well. According to the Mayo Clinic, even mild dehydration can drain your energy and make it harder to think clearly. That is not a comfort issue. That is your brain and your muscles quietly underperforming because the fuel line is running dry.

Most healthy adults need somewhere in the range of 11.5 to 15.5 cups of total fluid per day, and that includes water from food and other beverages. In a heat wave, you need more.

When it is 94 degrees with a heat index above 100, your body works overtime to keep your core temperature stable. The main tool it uses is sweat. As sweat evaporates off your skin, it pulls heat away from your body. That is beautiful engineering, but it comes at a cost: you are losing water and electrolytes every minute you are outside.

If you cannot replace those fluids fast enough, you slide into dehydration, and dehydration in the heat looks like this:

• Headache and dizziness
• Fatigue that does not lift with rest
• Dark yellow urine, or going hours without needing to go
• Muscle cramps
• Nausea, confusion, or a rapid heart rate in more serious cases

The Mayo Clinic notes that in extreme cases dehydration causes confusion and dizziness, and if you are vomiting, have a rapid heart rate, or feel like you might pass out, that is a signal to get medical help, not to power through.

Push further and you enter the territory of heat exhaustion and heat stroke, which are medical emergencies. Every summer, I see patients who were "just doing yard work" or "just at their kid's game" and ended up in real trouble because the heat crept up on them faster than they realized.

Here is what most people miss. Dehydration is not only a hydration problem. It is a heart problem.

When you are low on fluids, the volume of blood circulating through your body drops. Your heart has to beat faster and work harder to move that thinner supply through your vessels. Your blood pressure can swing, your kidneys strain to conserve water, and your circulation to the skin, the very system that was supposed to cool you down, gets less efficient.

For a healthy 30 year old on a Saturday hike, that usually means a bad afternoon. For someone with high blood pressure, heart disease, or diabetes, or for anyone on medications like diuretics, it can be genuinely dangerous. Heat and dehydration are quietly one of the most under-appreciated cardiovascular stressors we see in the summer.

Hydration is not just about feeling refreshed. It is one of the simplest things you can do to protect your heart in the heat.

If there is one thing I wish more of my patients understood, it is that your brain is often the first organ to complain about dehydration.

That mid-afternoon headache. The trouble focusing on a task that should be easy. The irritability that seems to appear from nowhere. Mayo Clinic points to headaches, difficulty concentrating, and impaired performance as some of the earliest signs that your fluid intake is not keeping up.

By the time you feel thirsty, you are already mildly dehydrated. Thirst is a late signal, not an early one.

This is why I tell patients to drink on a schedule in the summer, not on a feeling.

This is the practical part, and I want to keep it simple, because complicated advice does not survive a 100 degree afternoon.

Some people dehydrate faster and feel it harder. If you are in one of these groups, or you love someone who is, take the heat especially seriously this summer:

• Older adults, whose thirst signal weakens with age
• Young children, who do not always recognize or communicate thirst
• Anyone with heart disease, kidney disease, or diabetes
• People on diuretics, blood pressure medications, or certain psychiatric medications
• Pregnant and breastfeeding women
• Outdoor workers and athletes

Check on your parents. Check on your neighbors. Set a timer for your kids. The heat this summer does not care how tough you are.

Indiana summers ask something of your body, and this one is asking loudly. Heat pulls water out of you faster than you notice, and dehydration quietly taxes your brain, your muscles, your kidneys, and your heart before it ever announces itself with thirst.

The good news is that the fix is almost embarrassingly simple. Drink water on a schedule, not on a feeling. Add electrolytes when you are sweating hard or ill. Eat foods that hydrate you. Move your outdoor time to the edges of the day. And listen to your body when it tells you to slow down.

Your body is built to handle summer. Your job is to give it what it needs to do the work.

1. Mayo Clinic "Water: How much should you drink every day?" on daily fluid needs, signs of dehydration, and heat-related fluid loss. Read Source →
2. Northwestern Medicine "Do Electrolytes Really Boost Hydration?" on when electrolyte replacement is medically useful versus when plain water is enough. Read Source →
3. Indianapolis Star "Hoosiers to experience dangerous heat," on the 2026 Indiana heat wave, extreme heat warnings, and heat index readings across central Indiana. Read Source →