Eating can raise your blood pressure. Doctors may recommend taking your blood pressure before eating. Blood pressure may also fluctuate for other reasons, including exercising and having a full bladder.

Blood pressure is a measurement of the force of your blood pushing against your artery walls when it travels from your heart to the rest of your body. Blood pressure below 120/80 is normal. Blood pressure is generally considered low when it’s less than 90/60.

High blood pressure, called hypertension, increases the risk of heart attack and stroke. Low blood pressure, called hypotension, increases the risk of:

If you check your blood pressure at home, a number of factors can affect your blood pressure readings. Read on to learn how eating, not eating, diet, and other factors can affect these readings.

If your doctor has suggested measuring your blood pressure at home, it’s likely they’ve recommended you take your morning measurement before eating. That’s because the reading will often be lower than is typical following a meal.

When you eat, your body directs extra blood to the stomach and small intestine. At the same time, blood vessels that are distant from your digestive system narrow, and your heart beats harder and faster.

This action maintains the blood flow and blood pressure to your brain, extremities, and elsewhere in your body.

If your blood vessels and heart don’t respond correctly to the extra blood directed to your digestive system, blood pressure everywhere but the digestive system will decrease. This is called postprandial hypotension.

Postprandial hypotension can result in:

According to a 2010 research review, postprandial hypotension may affect up to 33 percent of older adults living in nursing homes.

Fasting can help lower blood pressure. It can also result in an electrolyte imbalance. That can make the heart prone to arrhythmias, or problems with the rhythm or rate of your heartbeat.

Discuss fasting with your doctor before trying it.

You can affect your blood pressure with diet.

If you have high blood pressure, you can lower it by altering what you eat. The Dietary Approaches to Stop Hypertension (DASH) diet can lower your blood pressure up to 11 mm Hg.

The DASH diet is low in saturated fat and cholesterol and rich in:

  • vegetables
  • fruits
  • low fat dairy products
  • whole grains

It is important to note the DASH diet also includes limiting salt and added sugars.

Reducing sodium can also lower blood pressure

Reducing sodium in your diet, even by a small amount, can reduce your blood pressure.

A 2015 study found the Mediterranean diet can lower blood pressure as well. It’s similar to the DASH diet, but higher in fat.

The fat in the Mediterranean diet is primarily monounsaturated fat from nuts, seeds, and olive oil. The study also suggested getting enough of the following may lower blood pressure:

  • potassium
  • magnesium
  • protein
  • fiber

If you’re monitoring your blood pressure at home, there are many factors that might affect the reading, including:

  • Exercise. Take your blood pressure before exercise or you might get an elevated reading.
  • Meals. In the morning, take your blood pressure before eating, as digesting food can lower your blood pressure. If you must eat first, wait 30 minutes after eating before taking a measurement.
  • Bathroom. A full bladder can give you an elevated reading. Empty it before taking a measurement.
  • Cuff size. If the monitor’s cuff doesn’t properly fit your upper arm, you may get inaccurate readings. Your doctor can tell you if your monitor’s cuff fits properly. If it doesn’t, they can show you how to position it for best results.
  • Clothing. For an accurate reading, don’t put the cuff over clothing; put it over bare skin. If you need to roll up your sleeve to the point it’s tight on your arm, take off your shirt or take your arm out of the sleeve.
  • Temperature. If you’re cold, you might get a higher than expected reading.
  • Position. For consistent and comparable results, always use the same arm and position it properly. It should be rested at the level of your heart on a chair arm or table. Your back should be supported and your legs should be uncrossed.
  • Stress. To get the most accurate reading, avoid stressful thoughts and sit in a comfortable position for 5 minutes before taking a measurement.
  • Talking. Avoid talking when taking your blood pressure, as it could elevate the measurement.

To make sure you’re getting accurate information, bring your home blood pressure monitor to your doctor’s office once a year. You can compare its readings with the readings from your doctor’s equipment.

Have your blood pressure checked as part of your regular doctor’s visits. When you’re ages 18 to 39, ask your doctor for a blood pressure reading every 3 to 5 years, if you are not at risk for high blood pressure and have a prior “normal” blood pressure reading.

If you have a high risk for high blood pressure, are overweight, or are over age 40, ask for a reading every year.

Call your doctor if you:

  • have a high blood pressure reading (above 120/80) and you haven’t received a diagnosis of hypertension
  • have well-managed blood pressure, but it measures above the “normal” range more than once
  • are concerned that your blood pressure medication is causing side effects

When to seek immediate medical attention

Seek emergency medical services if your blood pressure is markedly elevated with or without the following symptoms:

  • headache
  • dizziness
  • altered level of consciousness
  • nausea
  • vomiting
  • chest pain
  • shortness of breath
  • vision changes
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A number of factors can affect your blood pressure, including eating a meal. That typically lowers blood pressure.

If you have high blood pressure, a diet like the DASH or Mediterranean diet can help lower it.

It’s important for your doctor to monitor your blood pressure if your blood pressure is regularly too high or too low. Regularly high blood pressure increases the risk of heart attack and stroke and regularly low blood pressure increases the risk of heart and brain damage.

If your doctor has recommended that you monitor your blood pressure at home, a number of factors can affect the readings, such as:

  • measuring too soon after eating a meal
  • exercising
  • consuming alcohol, tobacco, or caffeine
  • having a cuff that doesn’t fit or is placed over clothing
  • not being relaxed and sitting in the proper position

By working with your doctor, you can get your blood pressure to a measurement that’s healthy for you.