In a world where your smartwatch puts activity, sleep, calories and heart rate at the forefront of your wellness journey, it's easy to overlook a silent health marker like blood pressure. But it's a significant indicator of your overall health that shouldn't be ignored.

Blood pressure is a measurement of the force of your blood pushing against your blood vessel walls. High blood pressure, also called hypertension, occurs when the pressure is consistently too high. The chronic effects include damage to the heart, blood vessels, brain, kidneys and more.

"It's important to periodically check your blood pressure because high blood pressure doesn't cause symptoms unless it's severely elevated," says Dr. Sadeer Al-Kindi, a preventive cardiologist at Houston Methodist. "This is why we consider it a silent killer, because high blood pressure can quietly increase the risk of heart attack, stroke, heart failure and other cardiovascular issues."

In other words, if you're waiting for signs that your blood pressure is high, you're waiting too long. Here's everything you need to know to keep proper tabs on yours.

What's a good blood pressure?

Blood pressure is measured as two numbers: a top number (systolic blood pressure) and a bottom number (diastolic blood pressure). Both are measured in millimeters of mercury (mm Hg).

"Systolic is the pressure of the blood as the heart is contracting, whereas diastolic is the pressure when the heart is relaxed," explains Dr. Al-Kindi. "Both numbers are important when considering a healthy blood pressure."

So, what's a good reading? Normal blood pressure is anything lower than 120/80 mm Hg.

"The closer blood pressure is to those numbers, the healthier," adds Dr. Al-Kindi. "If it's elevated beyond that, we start to worry about high blood pressure."

What is considered high blood pressure?

There are four stages of concerning blood pressure levels: elevated, high blood pressure stage 1, high blood pressure stage 2 and hypertensive crisis. These stages are defined by the following blood pressure ranges:

• Elevated blood pressure: 120-129/80 mm Hg
• High blood pressure stage 1: 130-139/80-89 mm Hg
• High blood pressure stage 2: 140/90 mm Hg or higher
• Hypertensive crisis: 180/120 mm Hg or higher*
  *Consult your doctor immediately

If blood pressure is elevated, it's important to take action. Lifestyle changes can help prevent elevated blood pressure from progressing to high blood pressure, a point at which medications are often needed to help manage the condition.

(Related: How to Lower Blood Pressure Without Medication)

"For stage 1 high blood pressure, lifestyle changes are critical, and, depending on the individual, we also consider treatments to help lower blood pressure," says Dr. Al-Kindi. "For stage 2 high blood pressure, at least one medication is almost always needed to help get blood pressure under control. Lifestyle changes of course remain important."

How often should you check your blood pressure?

You know what's considered normal and high, but how closely do you need to monitor your numbers? The answer depends on your overall health. People who already have high blood pressure will need to monitor it more often than people who don't.

"For people who don't have a diagnosis or any conditions that increase high blood pressure risk, I think it is sufficient to check your blood pressure just once per year," says Dr. Al-Kindi. "There is no defined frequency in this case, but the more you check it the better — especially if you have a family history or high blood pressure or are at higher risk. There's also no harm in checking it more frequently."

Factors that increase a person's risk of high blood pressure include:

• Increasing age
• Being overweight
• Eating a high-salt diet
• Being African American
• Having certain chronic conditions, including diabetes, sleep apnea and kidney disease

How to check your blood pressure

Monitoring your blood pressure is quick and easy. From kiosks at pharmacies to health fairs at work or your annual appointment with your primary care doctor, there are plenty of opportunities to get your blood pressure measured.

"The vast majority of blood pressure machines available to the general public have gone through testing and validation to be as accurate as possible," says Dr. Al-Kindi. "That said, the way you measure your blood pressure can affect accuracy and become problematic. There are specific steps we recommend following to get the most accurate reading."

When checking your blood pressure, be sure that:

• You stay relaxed, including avoiding talking
• The blood pressure cuff is contacting your skin, not over clothing
• The blood pressure cuff is snug, but not overly tight
• Your arm is resting at chest height, not above or below
• You're seated in a chair that supports your back
• Your feet are flat on the floor

"There are also factors to consider before checking your blood pressure, to help get your body in a relaxed state," says Dr. Al-Kindi. "You'll want to empty your bladder first and avoid eating or drinking in the 30 minutes beforehand, especially caffeine since this can cause short-lived but dramatic increases in blood pressure. The goal is to reduce noise like this that can cause inaccurate readings."

You might also wonder if there's a best time of day or preferred arm for your readings. Dr. Al-Kindi recommends measuring your blood pressure in the morning, if able, and says that it generally doesn't matter which arm you use.

If your blood pressure is elevated, taking a few readings can help confirm the numbers. Continually high readings should prompt you to schedule an appointment with your primary care doctor to have your blood pressure more thoroughly evaluated.

"The good news is that, if your blood pressure is elevated, we have very effective ways of lowering it," adds Dr. Al-Kindi. "Once we get high blood pressure under control, the risk of these serious outcomes gets eliminated. It's another reason why periodically monitoring it is so important."