Can dehydration cause high blood pressure?

Yes! dehydration can cause high blood pressure although not a very common occurrence. The link between dehydration and high blood pressure needs further investigation.

---

Introduction

Dehydration is more common than you may like to think of it. It has been reported that about 17% to 28% of adults in America are dehydrated and dehydration results in frequent hospital admission of most people [source].

Since high blood pressure is a common cause of admission, it is in order for you to ask the question “Can dehydration cause high blood pressure”.

High blood pressure is a term used commonly for the medical condition of hypertension. Hypertension is technically when there is persistently high blood pressure. It is a long-term condition in which the force of your blood is greater than normal and pushes hard against the walls of your blood vessels. 

High blood pressure, if left untreated, can lead to a variety of significant health concerns, including heart attack and stroke. High blood pressure can be caused by a variety of circumstances. Dehydration has been named as having the potential to produce high blood pressure.

In this article, we will take a closer look at the link between dehydration and high blood pressure.

---

What is dehydration?

Dehydration occurs when your body does not have enough water to function properly. Up to about 60% – 75% of the human body is made up of water [source]. Hence water is very essential to the functions of the body.

Your body will not work correctly if you don’t get enough water. Depending on how much fluid is lacking from your body, you can have mild, moderate, or severe dehydration.

With mild dehydration, it can be treated easily at home. Severe dehydration requires emergency medical treatment. 

---

Causes of dehydration?

Your body loses water every day and it is perfectly normal. We lose water every day by sweating, breathing, tears, saliva, peeing, and even pooping. 

The water lost is replenished when we take in fluids or consume foods with high water content. Below are some of the common causes of dehydration.

Excessive sweating

Sweating is the body’s way of cooling down when it gets overheated. When the body becomes hot, the sweat glands activate to release moisture from the body. This release enables the body to cool off. This is accomplished through evaporation.

A drop of perspiration carries a small quantity of heat with it as it evaporates from your skin. The more sweat you create, the more evaporation occurs, and you get cooler.

Sweating also moisturizes your skin and keeps your body’s electrolyte balance in check. Salt and water make up the majority of the fluid you sweat.

Excessive sweating can lead to dehydration because you lose so much water. Hyperhidrosis is the medical word for excessive perspiration.

Vomiting

Vomiting can cause the body to lose too much water. Electrolytes (minerals used by the body to control muscles, blood chemistry, and organ processes) are lost when you vomit.

This can lead to the functions mentioned above being hindered which can lead to serious effects such as coma and stroke. 

Diarrhea 

Another cause of dehydration is diarrhea. Diarrhea is a condition that causes your bowel movements to become loose and watery.

You could become dehydrated if you have watery stools more than three times a day and don’t drink enough fluids. If not addressed, this can become a significant problem.

Fever

When you have a fever, your body attempts to lower your temperature by losing fluid through your skin’s surface.

When you have a fever, you may sweat excessively, and if you don’t drink to restore your fluids, you may become dehydrated.

Excessive peeing

Urination is the body’s natural mechanism of eliminating poisons. Chemical imbalances might result from certain situations, which can lead to an increase in urine production.

You risk dehydration if you don’t replace the fluid lost through excessive urine.

---

Signs and symptoms of dehydration.

Dehydration symptoms vary depending on whether the disease is moderate or severe. Dehydration symptoms may arise before total dehydration has occurred.

Symptoms of mild and moderate dehydration include

• Thirst
• Dry or sticky mouth
• Not peeing very much
• Dark yellow pee
• Dry, cool skin
• Headache
• Muscle cramps

Symptoms of severe dehydration include

• Dizziness
• Rapid heartbeat
• Fainting
• Rapid breathing
• Very dry skin
• Dark yellow pee
• Low blood pressure
• Lack of sweat production
• Excessive thirst 

---

What is blood pressure?

Blood pressure is the force of blood pushing against the walls of blood vessels. Blood is pumped from the heart into blood arteries, which carry it throughout the body.

Blood pressure can be classified as low (hypotension)  normal (normotension), and high (hypertension). 

Two major factors affect blood pressure. They are the resistance offered to the flow of blood through the vessels (total peripheral resistance) and the amount of blood the heart pumps through the circulatory system in a minute (cardiac output).

The latter is also affected by two factors which are the rate at which the heart is working (heart rate) and the volume of blood being in and out of the heart (stroke volume).

Hence any other parameter in the body that can affect either total peripheral resistance, heart rate, or stroke volume can directly or indirectly affect the blood pressure.

Dehydration which leads to a decrease in the amount of water in the body can result in a decrease in blood volume.

So, the question is, will dehydration lead to a decrease in blood pressure or an increase instead?

---

Low blood pressure 

When your blood pressure reading is less than 90/60 mmHg, you have low blood pressure. 

Since blood pressure is equal to the product of cardiac output and heart rate, it decreases when cardiac output decreases. Cardiac output is directly proportional to the blood volume, hence when blood volume decreases, cardiac output will decrease.

Dehydration which usually leads to a decrease in blood volume and consequently leads to a decrease in cardiac output will result in low blood pressure.

Blood must be able to reach all of your body’s tissues, therefore maintaining a normal blood volume is essential. When you are dehydrated, your blood volume drops, which causes your blood pressure to drop. 

Your organs will not receive the oxygen and nutrients they require if your blood pressure goes too low. It’s possible that you’ll fall into shock.

---

High blood pressure

When your systolic (top number) blood pressure is 140 mm Hg or higher, and your diastolic (bottom number) blood pressure is 90 mm Hg or higher, you have high blood pressure. It is recommended that you see a doctor if you are suffering from high blood pressure. 

Causes of high blood pressure 

Persistent high blood pressure known as hypertension is a serious health issue and should not be taken lightly. High blood pressure can make the heart work harder in order to pump blood out to all parts of the body. 

It may also lead to stroke, heart failure, and other complications if not controlled adequately. Below are some of the factors known to be implicated in persistent high blood pressure.

• Stress
• Old age
• Genetics
• Excessive alcohol intake
• Lack of physical activity
• Too much salt in diet
• Obesity
• Smoking
• Family history of high blood pressure
• Chronic kidney disease

---

Can dehydration cause high blood pressure?

Yes, dehydration has been found to cause high blood pressure in some cases although the actual link needs further investigation.

One hypothesis that supports dehydration causing high blood pressure is that there is a reflex reaction induced by the body in response to dehydration which can result in an increase in blood pressure.

This reflex is essential for survival in emergency cases. When your blood pressure drops so low, you may end up in a shock which can lead to death. To prevent this, the body tries to compensate and increase blood pressure.

How does it do that then?

How dehydration may lead to an increase in blood pressure

When you become dehydrated, the blood volume goes down, and you may have a lot of solutes in the blood. A higher concentration of sodium may be detected in the blood.

During filtration through the kidneys, the body detects the high solute concentration and releases a hormone called vasopressin. Vasopressin aids water retention in the kidneys, preventing you from losing more water through pee. 

At the same time, it causes your blood vessels to tighten, resulting in an increase in blood pressure. 

So, in summary, dehydration may result in an increase in blood pressure through the stimulation of the release of vasopressin which increases blood volume and total peripheral resistance leading to an increase in blood pressure.

Can dehydration cause low blood pressure?

Dehydration can cause your blood volume to decrease (the amount of fluid in your blood vessels).

Unlike when dehydration causes an increase in blood pressure, the decrease in blood pressure is more common and is likely to be experienced by most people with dehydration.  

A regular blood volume is critical because it permits your blood to reach all of your body’s tissues and organs. A low blood volume, on the other hand, can cause your blood pressure to plummet. 

Dehydration can cause your blood volume and blood pressure to dip dangerously low. This can make it difficult for your tissues and organs to acquire the oxygen and nutrients they require to stay healthy. 

Low blood pressure, if left untreated, can lead to various problems, such as heart problems, brain damage, and even sudden deaths.

---

The takeaway from this article

Dehydration can cause high blood pressure. However, you may be able to prevent high blood pressure from dehydration by ensuring adequate hydration on a regular basis. 

You should also adopt a healthy lifestyle and drink lots of fluids. If you are sick, in a hot climate, or doing physical activity, ensuring adequate hydration is extremely vital.