Why your blood pressure numbers go haywire in the summer

In this article:

• Does heat affect blood pressure?
• Blood pressure meds causing heat intolerance
• Feeling hot from blood pressure meds
• Medication adjustments
• Alternatives
• Working in the heat
• Safety

In this article

• Does heat affect blood pressure?
• Blood pressure meds causing heat intolerance
• Feeling hot from blood pressure meds
• Medication adjustments
• Alternatives
• Working in the heat
• Safety

Your blood pressure numbers may be perfect, then suddenly, summer rolls around, and your numbers are all over the place. What is causing this change? It’s not in your head; the summer heat can affect blood pressure in several ways. 

Does summer heat affect blood pressure?

Summer heat may cause your blood pressure to vary, but not everyone will be affected in the same way. And the changes you may see can be related to the temperature and humidity. When the temperatures and humidity are higher, you may see more of an effect on blood pressure. Experts note that some people tend to have lower blood pressure in the summer because the heat leads to increased blood flow. Some people are more susceptible to the effects of heat and humidity, such as older adults, those who have obesity or are overweight, and individuals with heart, lung, or kidney problems. Heat and sweating can also lead to dehydration, which can make it harder for the body to function normally. Taking medicine for hypertension (high blood pressure) can also play a role in your blood pressure readings in the summer. Your healthcare provider can give you individualized medical advice on how to monitor and manage your blood pressure in the warmer months.

Which blood pressure medications cause heat intolerance?

There are many different blood pressure medications, each belonging to a broader class of drugs. The most common classes of blood pressure drugs include diuretics (water pills), beta blockers, angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), and calcium channel blockers. The effects of blood pressure medicines can be influenced by heat and sun. Many people take more than one type of blood pressure medication, so the effects may be increased. Other medications, such as antihistamines, tricyclic antidepressants, or antipsychotics, can also be affected by heat. Talk with your healthcare provider about the heat-related risks with the medication(s) you take.

How common blood pressure meds interact with summer heat
Drug class	Common examples	How it interacts with heat	Main risks
Diuretics	Furosemide Hydrochlorothiazide Torsemide	Diuretics help the body eliminate fluids in the urine, but in hot weather, the effects can be intensified. This increases the risk of dehydration and electrolyte imbalance. Diuretics can also increase sun sensitivity or photosensitivity, and some diuretics are associated with certain types of skin cancer.	Dehydration Electrolyte imbalances Low blood pressure Risk of fainting and falls Skin reactions, sunburn, and skin cancer
Beta blockers	Atenolol Metoprolol Nebivolol Propranolol	Beta blockers may affect the body’s ability to regulate its temperature, making it harder to cool off in the heat. They can also reduce your sense of thirst, increasing the risk of dehydration.	Overheating or heat-related illness Dehydration Low blood pressure Risk of fainting and falls
ACE inhibitors	Enalapril Lisinopril Ramipril	ACE inhibitors may decrease the sensation of thirst, which can lead to dehydration. They can also increase the risk of low blood pressure, which can lead to fainting and falls.	Low blood pressure Risk of fainting and falls Dehydration
Angiotensin receptor blockers (ARBs)	Losartan Olmesartan Valsartan	ARBs may reduce the sensation of thirst, potentially leading to dehydration. They can also increase the risk of low blood pressure, which can lead to fainting and falls.	Low blood pressure Risk of fainting and falls Dehydration
Calcium channel blockers	Amlodipine Nifedipine	Calcium channel blockers may affect the body’s ability to regulate temperature, making it harder to cool off in the heat. They can also reduce your sense of thirst, increasing the risk of dehydration.	Overheating or heat-related illness Dehydration Low blood pressure Risk of fainting and falls

Can blood pressure medicine cause you to feel hot?

Yes, in some cases, but for different reasons. 

Some blood pressure medications may cause flushing as a side effect. This is more common with some, but not all, calcium channel blockers, such as amlodipine, nifedipine, or felodipine. If you have skin flushing, you may notice a sudden but temporary feeling of warmth, usually in the face, neck, or upper chest. Your skin may turn red or darker, and you may sweat. 

Other medications can interfere with the body’s cooling mechanisms, which can make it harder for your body to cool down when it’s hot outside. This can cause symptoms like nausea, weakness, headache, and dizziness, and increase the risk of heat-related illness. Beta blockers and some calcium channel blockers can do this. Diuretics may cause dehydration, which can also make it harder for the body to cool down.  

If you notice any of these symptoms, call your healthcare provider. Do not stop your medicine or change your dose on your own. 

Should I reduce my blood pressure medication dose in summer?

Some people will notice that their blood pressure is lower in the summer. In the summer, the blood vessels may widen, which may lead to lower blood pressure. And if you are already taking medicine to lower your blood pressure, the effects may be even more noticeable. On the other hand, some people may experience the opposite effect. For example, dehydration may lead to an increase in blood pressure in some people.

Because not everyone will see the same effects from heat exposure, your healthcare provider may recommend regularly monitoring your blood pressure at home. It is important to control your blood pressure throughout the year to reduce the risk of a heart attack and stroke. If your blood pressure tends to vary in the hotter months, your healthcare provider may recommend a temporary dosage adjustment. However, you should not attempt to adjust your medication dosages on your own. Always follow the guidance of your healthcare provider.

Are there blood pressure medications that cause less heat sensitivity?

Many blood pressure medications can affect how your body responds to the heat. There is no one “best” medication for people who are concerned about the effects of heat. It’s best to talk to your healthcare provider about which medication is appropriate for you. They can give you medical advice based on individual considerations such as your age, chronic conditions, and other medications you take. 

Blood pressure medication and working in the heat

What if you work outside? Outdoor workers, such as construction workers, landscapers, farmers, and lifeguards, may be particularly concerned with heat exposure. People who work in hot indoor environments, such as kitchen workers, or anyone else with heat exposure at work, may also be concerned. People who spend frequent or longer stretches of time in the heat may be more susceptible to its effects than people who spend shorter periods of time in the heat (i.e., an occasional day at the beach). Also, people who take medication to treat high blood pressure may be more susceptible. 

The Centers for Disease Control and Prevention (CDC) provides recommendations for those who work in environments with heat stress, such as workplace training, using a buddy system, and monitoring weather reports.

If you take medication for high blood pressure, you should be alert to early warning signs of heat-related illness, such as nausea, muscle cramps, heavy sweating, irritability, headache, weakness, dizziness, lightheadedness, and fainting. If you work in the heat, talk to your healthcare provider ahead of time about precautions you can take and what to do if you start to experience symptoms. You may also want to discuss workplace safety precautions with your employer.

How to stay safe on blood pressure medication this summer

Check in with your healthcare provider before the summer months. Ask if there are any specific precautions you should take or dosage adjustments that you need to make. Here are some tips on staying safe in the summer:

• Avoid being outside during the hottest hours, typically between 10 am and 4 pm.
• Stay cool; spend time in the air conditioning when possible.
• Drink plenty of water to stay hydrated. Ask your healthcare provider how much water you should drink, as everyone’s needs may vary depending on medical conditions and medications you take. 
• Wear clothing that is loose, lightweight, and light colored.
• Use broad-spectrum sun protection of SPF 30 or higher if you are outside, and reapply frequently.
• If you do need to spend time outside, take frequent breaks in the shade or inside in air conditioning.

It’s also important to remember to store your medications safely in the summer. Medications such as insulin and GLP-1s are especially susceptible to extreme temperatures and have specific storage requirements. However, all medications have storage requirements to be mindful of. For medications that require room temperature storage, store them in a cool, dry place, away from heat and humidity. Avoid storing medicines in the bathroom or car.

Be alert to symptoms of heat-related illness, because symptoms can get more severe and life-threatening if left untreated. 

• The first symptoms may include muscle cramps and spasms, often in the stomach or legs. If this happens, get out of the heat, gently massage muscles, and sip water. Get medical attention if cramps last more than one hour. 
• Symptoms of heat exhaustion may include heavy sweating, weakness, muscle cramps, nausea, vomiting, headache, clammy skin, dizziness, and fainting. If these symptoms occur, go to an air-conditioned room right away, loosen your clothing, drink sips of water, and apply cool, wet cloths. Get medical attention right away if you are vomiting or if symptoms become worse or last more than one hour. 
• Heat stroke is a medical emergency. Symptoms of heat stroke may include throbbing headache, confusion, slurred speech, nausea, dizziness, fainting, and loss of consciousness. If this happens, call 911 and move to an air-conditioned environment if possible, while waiting for help. 

RELATED: Supplements for heat intolerance

Expert takeaway 

“Heat and sun exposure can affect people differently, so be sure to check with your healthcare provider about your risks, and how to monitor and manage your blood pressure during the summer,” says Karen Berger, Pharm.D., a member of SingleCare’s Medical Review Board.