How Does Dehydration Affect Your Blood Pressure?

Dehydration causes more symptoms than thirst. This common condition, which is actually a body-wide problem, can cause many symptoms, including both high and low blood pressure. Many reports estimate that older adults are especially vulnerable to inadequate hydration, with up to 28% struggling with chronic dehydration.

Wondering how dehydration affects blood pressure is common — after all, blood is mostly water. Normal blood pressure for an adult is around 120/80 mm Hg, while normal blood pressure for a child is calculated by age. The high end of blood pressure charts may range from 60/31 mm Hg for a female infant to 131/83 mm Hg for an adolescent male. When the body is dehydrated, it can put a strain on the heart, as it has to pump faster to circulate blood throughout the body.

What happens when there’s not enough water in the body? Learn about how dehydration affects blood pressure, how proper hydration can help, and when it’s time to seek medical help for blood pressure problems related to dehydration.

How Dehydration Affects Your Blood Pressure

Not drinking enough water can cause high blood pressure, as dehydration causes changes in the blood. It also ultimately stresses the heart. Here’s a basic overview of how the physiology of dehydration works:

1. Your body loses water. This happens little by little through normal activities such as sweating, urinating, and even breathing. Dehydration speeds up with more vigorous physical activity or illness that causes vomiting, diarrhea, or night sweats.

2. Your blood volume decreases. Because blood is mostly composed of water, dehydration means that your blood becomes thicker, stickier, and more concentrated.

3. Your heart responds. If you feel that you have a faster heartbeat when you’re dehydrated, you’re not imagining this. The heart will try to stabilize your body by pumping harder.

Mild to moderate dehydration often leads to higher-than-normal blood pressure. This happens because the blood vessels constrict and the heart has to work harder to pump thicker, more viscous blood around the body. In this case, you may be able to treat the problem at home by drinking an adequate amount of water or hydrating with an electrolyte drink. In more serious situations, you may need medical intervention.

Does Dehydration Also Cause Low Blood Pressure?

Dehydration can also cause low blood pressure due to the lack of water in your blood. The more dehydrated you become, the more your blood volume decreases. This might happen before you notice any symptoms.

While you might experience high blood pressure temporarily due to dehydration, when you’re more severely dehydrated, your blood pressure will drop lower. Warning signs may include clammy, pale skin, a weak pulse, confusion (usually in older adults), and rapid breathing.

Signs of Dehydration Affecting Your Blood Pressure

It’s not always easy to recognize the signs of dehydration or blood pressure issues — especially when you think you are drinking enough water. It can trigger clear warning signals like thirst, but it can also cause muscle pain and other not-so-obvious symptoms. Look out for the following signs of dehydration that could correlate with blood pressure changes:

• Dizziness: Low blood pressure due to dehydration can cause lightheadedness and vertigo due to the lack of fluids and oxygen circulating to the brain.
• Rapid heart rate: You’ve learned that when you’re dehydrated, the heart beats faster and stronger to try to circulate your blood. Don’t assume that this signifies high or low blood pressure. It may be either one.
• Dark urine: You may notice darker, more concentrated urine before you notice other signs of dehydration, especially when you’re ill.
• Headache: As your body loses fluid, your brain and other related tissues contract. When this shrinkage puts pressure on the surrounding nerves in your head, this causes a headache. If you’re prone to getting this type of headache with low blood pressure, you may also feel dizzy.
• Fatigue: When the body doesn’t get the fluid it requires to function, you may feel tired or lethargic. Low blood pressure can also cause a feeling of fatigue or nervousness, while a sudden drop in blood pressure can even cause a sudden feeling of impending doom.

Dehydration can cause several alarming symptoms. However, they all stem from the lack of enough fluid circulating through the body. In early stages, you can correct the problem by drinking water or an electrolyte drink. If you’re experiencing any of these symptoms for the first time, or you’re not able to rehydrate as usual, it’s time to get it checked out by a medical professional.

What Causes Dehydration?

Sometimes it’s easy to pinpoint what caused your dehydration. Other times, it’s not so clear-cut. Consider one scenario in which a person has a stomach illness that causes vomiting and another where her friend travels to a high-altitude location without hydrating along the way.

Over time, these two people may become similarly dehydrated, struggle with headaches and dizziness, and ultimately develop issues with their blood pressure. However, the first person may be quicker to attribute these symptoms to dehydration because she is already ill and knows she is losing fluids.

If you’re wondering if you are experiencing blood pressure symptoms that may be related to dehydration, consider whether you’re dealing with:

• A recent illness that caused vomiting, diarrhea, or night sweats
• Taking certain medications for diabetes, blood pressure, or chemotherapy that affect how much water leaves your body — diuretics and laxatives can cause dehydration, too
• Travel to, or living in, a hot climate

Some people experience high diastolic blood pressure (the bottom number in the blood pressure reading) due to lifestyle and genetic risk factors. You may be predisposed to diastolic hypertension if you’re male or an older adult. You’re also at risk if you have diabetes, hypothyroidism, or kidney disease.

Can Drinking Water Help Lower High Blood Pressure?

Drinking water can certainly help lower blood pressure if the main cause is dehydration. However, chronic hypertension often requires further treatment. Drinking lots of water may lower blood pressure temporarily, especially if the dehydration was caused by a specific event (like vomiting or heat exposure).

Can dehydration cause high blood pressure that doesn’t improve? If you aren’t sure why you’re often dehydrated or why you struggle to bring down your blood pressure, it’s best to get evaluated by a medical professional. This especially applies if you have any warning symptoms like the ones listed in the previous sections.

When To Seek Urgent Care for Blood Pressure Concerns

The best solution for preventing blood pressure problems due to dehydration is simple — staying hydrated. However, this isn’t always possible. It’s not always easy to recognize when you become dehydrated for various reasons. Maybe you completed a more intense workout than usual, you’re dealing with uncomfortable night sweats due to sickness or perimenopause, or perhaps you just landed after a 12-hour flight.

Dehydration can quickly evolve from a minor annoyance into a serious medical situation. Signs in adults that warrant urgent care evaluation include very high blood pressure readings, rapid heart rate, and dehydration symptoms that don’t improve with fluids.

If you’re experiencing these symptoms, or anything else that concerns you, find a Next Level urgent care location near you as soon as possible. Our team of experienced clinicians can assess the problem and help you make a plan to avoid this uncomfortable situation in the future.