Why Does Your Blood Pressure Spike In The Afternoon And Evening?

Have you ever wondered why your blood pressure is higher in the afternoon and evening and low at night? Have you ever experienced a spike in blood pressure at the doctor’s only to get a normal reading when you’re back at home? It’s normal for blood pressure to rise and fall throughout the day, but some patterns indicate there’s a problem.

Slightly fluctuating blood pressure isn’t usually cause for concern, but it can make it challenging to get an accurate reading or recognize when something’s up. Untreated, significant fluctuations can increase your risk of developing serious health problems and damaging your cardiovascular system.

Why does blood pressure fluctuate?

Blood pressure fluctuates throughout the day for several reasons, but it’s helpful to know what to expect and when your fluctuating blood pressure might be abnormal.

Circadian rhythms

Your blood pressure is strongly influenced by your body’s circadian rhythms, including your natural sleep cycle. Your circadian rhythm is connected to the master clock in your brain which regulates your body function throughout the day.

As the sun goes down and it gets dark, your master clock tells you it’s time to go to bed and get some rest. In contrast, when the sun is up, your master clock makes sure you have enough energy to stay alert and go about your day. Your heart rate and blood pressure will adjust according to this pattern,¹ so it’s normal for your blood pressure to dip while you sleep and rise throughout the day.

Physical activity

Being active and exercising regularly helps reduce your risk of developing high blood pressure in the long term. For people with diagnosed hypertension, exercise has been found to cause a blood pressure dip called postc-exercise hypotension (PEH).

You might notice your blood pressure reading change slightly during or after exercise. This is normal, but a significant change could suggest you have hypertensive response to exercise (HRE).² In HRE, blood pressure in normal, healthy people elevates significantly with exercise (systolic blood pressure rises to 210mm Hg for men and 190mm Hg for women or higher). HRE is thought to be an early warning sign for developing hypertension.

Nervousness and stress

When you feel nervous or stressed, your body enters “fight or flight” mode and releases more of the hormones adrenaline and cortisol. When this happens, your heart rate rises and your blood vessels narrow (vasoconstriction), raising your blood pressure temporarily. This is a normal response from your body.

White-coat syndrome

Have you ever wondered why your blood pressure reading is normal at home and rises at the doctors? This is white-coat syndrome, and it occurs when you feel stressed about visiting your doctor or being in a clinical environment. A high reading caused by white-coat syndrome doesn’t always mean you have hypertension.

Eating and drinking

Consuming food and drink affects your blood pressure, with some foods having more of an influence than others. While it’s normal for blood pressure to drop slightly when you are digesting food after a meal, caffeine³ and foods containing added sugar⁴ have been shown to temporarily elevate blood pressure.

Eating salty foods⁵ has also been shown to elevate blood pressure as it increases water retention and the pressure on your blood vessel walls.

Medication

Some common medications like non-steroidal anti-inflammatory drugs (NSAIDs) and decongestants can also elevate blood pressure.

What if you have an unusual schedule?

Some people don’t follow a "typical" daily schedule where they’re awake when it’s light and asleep when it’s dark, perhaps because they work night shifts or their work rota changes. But how does this affect blood pressure?

A study⁶ showed that in people who reversed their routine (for example, by working at night and sleeping during the day), their daily rhythm adapted. Their blood pressure started to drop during the day and rise at night when they were awake.

However, sleep quality was found to be lower for night shift workers which can cause blood pressure complications. 

Another study⁷ suggested that poor-quality sleep negatively impacts the normal blood pressure dip, while a bad night’s sleep can cause a blood pressure spike when you wake up. These effects are risk factors for high blood pressure.

It’s important to note that not all studies support this argument — one study⁸ concluded shift work does not cause high blood pressure. This might suggest that some people adapt more easily than others, and sticking to a reversed schedule and avoiding rotating shifts (if you can) could make it easier for your body to adjust.

Tips for taking an accurate blood pressure reading

You might be asked to monitor your blood pressure with a machine you can use at home. But since blood pressure fluctuates throughout the day, is there a best time to take a reading?

Follow these recommendations to get an accurate blood pressure reading:

Measure your blood pressure at the same time each day

A good first step is to check your blood pressure at the same time every day to help even out fluctuations. You should also try to arrange appointments with your doctor at the same time of day.

Sit in the best position

Sit upright with your feet flat on the floor and your arm supported at the level of your heart (rest it on a table or pillow). Use the same arm each time you check your blood pressure. Resist the urge to talk or do other activities while your blood pressure is being taken.

Take a reading twice a day

Some experts suggest checking blood pressure twice a day: when you first get up and in the evening after work. This would be the opposite if you work night shifts. Taking a blood pressure reading twice a day will also help you detect any abnormal fluctuations.

Wait 30 minutes after eating, drinking, smoking, or exercising

Leaving some time before you take a blood pressure reading after eating, drinking (including alcohol and caffeine), smoking or exercising can allow your blood pressure to stabilize.

Keep a record of your readings

Keeping a record of your blood pressure readings is a good way to get an accurate, average measurement and highlight any unusual patterns. High blood pressure is not diagnosed after one high reading; your doctor will assess your average blood pressure, so being able to show them a blood pressure log will be helpful.

Here are some additional tips that can help you get an accurate reading:

• Place the cuff on your bare skin, not over your clothes

• Use a cuff that fits your arm — if it’s too small, it could falsely raise your blood pressure

• Make sure your bladder is empty before checking your blood pressure

Is there a problem with my daily blood pressure pattern?

It’s normal for your blood pressure to rise and fall throughout the day depending on your activities. You might expect to see a dip at night and pressure gradually rising through the afternoon and evening according to your circadian rhythm.

Severe or unusual fluctuations suggest your daily blood pressure pattern is abnormal. This is dangerous if you have been diagnosed with hypertension and increases your risk of developing the condition if you don’t already have it.

Too much fluctuation

A study⁹ found that daily blood pressure fluctuation is higher in people with diagnosed high blood pressure and that too much fluctuation damages the artery walls. If your blood pressure fluctuates significantly or at unexpected times, you might have high blood pressure.

Labile hypertension is the medical term for blood pressure that rises suddenly and significantly, causing serious complications.

It’s not always easy to diagnose, as your blood pressure might be normal when you take a measurement.

If your doctor believes you might have labile hypertension, they might ask you to monitor your blood pressure at home and take multiple readings at different times of the day.

Blood pressure not falling at night

In people with healthy blood pressure, blood pressure dips by 10–20% at night. This is because the system slows down and the heart doesn’t beat as hard.

If at-home monitoring reveals your blood pressure doesn’t drop at night or it gets higher, this suggests you have nocturnal hypertension.¹⁰

Ongoing nocturnal hypertension can cause cardiovascular problems, cognitive dysfunction, chronic kidney disease, falls, stroke, and organ damage, so many doctors now recommend taking certain blood pressure medications before going to bed.

Nocturnal hypertension is difficult to spot as blood pressure readings are typically taken during the day, and it can only be detected when you wear a blood pressure monitor at night.

Blood pressure rising or not dipping at night is also a symptom of obstructive sleep apnea¹¹ (OSA). Snoring or morning fatigue are typically used to diagnose OSA, so it is often missed in people who sleep alone.

If home monitoring shows your blood pressure doesn’t drop at night, your doctor might suggest a sleep study to check for OSA, which tends to aggravate or be aggravated by hypertension.

Although the link is still unclear, non-dipping nighttime blood pressure might suggest you have another sleep disorder, such as insomnia. Treating sleep disorders can help reduce the risk of heart problems and restore a normal dipping pattern.

A study¹² found that exercising in the evening may help lower nighttime blood pressure, as long as it doesn't interfere with sleep. Your doctor might recommend exercising in the evening if you have hypertension or nocturnal hypertension.

Blood pressure dropping too low at night

Some people’s blood pressure drops too low¹³ while they sleep, which is often followed by a larger than normal blood pressure spike in the morning. This is a warning sign for risk of stroke and ischemia (when your heart doesn’t get enough blood).

If your blood pressure is too low when you wake up, you may become dizzy or faint when you try to get out of bed. This is called orthostatic hypotension.

Your blood is circulating as normal when you lie down but is unable to reach your brain when you stand up. It can increase your risk of falls and injury, especially if you are older. It can also increase your risk of stroke.

These problems can be treated by adjusting your blood pressure medication or the time you take it.

Is it possible to stabilize blood pressure and reduce fluctuations?

Blood pressure fluctuations can make it challenging to take an accurate, meaningful reading, and severe fluctuations can increase your risk of health problems. You might be wondering if there's anything you can do to reduce this variability and stabilize your blood pressure.

Your first priority should be to continue taking your medication as directed. Your blood pressure should stabilize with effective treatment, so talk to your doctor if you’re concerned about your readings.

If medication is ineffective, you might have resistant hypertension (high blood pressure that doesn’t respond to treatment) or an underlying health condition.

Your doctor can make specific suggestions depending on your individual symptoms and how your blood pressure fluctuates. This might include taking your blood pressure medication (except diuretics) at bedtime to reduce nighttime blood pressure, taking them in the morning if your blood pressure is dropping too low, or exercising at a different time of day.

If you have resistant hypertension, there are surgical treatments available as a last-resort option.

The lowdown

Blood pressure naturally drops at night, increases through the day, peaks at midday, and stays high through the afternoon before decreasing in the evening. This is affected by the circadian rhythm among other factors, like exercise, food and drink, and stress. Shift workers might see a reversed pattern.

People with hypertension often experience wider fluctuations, although these generally stabilize with treatment. Your blood pressure should dip at night —if it doesn’t, you need to speak to your doctor about medication or adjusting the medication you are currently taking.

Ambulatory monitoring (wearing a blood pressure monitor for 24 hours) is the only way to assess your daily blood pressure fluctuations. To get an accurate reading, take multiple measurements at the same time each day and wait 30 minutes after exercising, eating, drinking, or smoking.