Blood pressure log: how to keep one your doctor can use

Short answer

One reading is not a measurement. Guidelines ask for two readings a minute apart, morning and evening, for at least three days and ideally seven — then the average. Record date, time, both numbers, pulse and anything unusual. Home readings use a different threshold from office readings.

If your readings at home look nothing like the one taken at the surgery, you were not imagining it. That gap has a name, it is common, and finding it is the main reason logs exist.

Note: this is general health information, not medical advice, and it does not replace your clinician's assessment. Guideline figures below are cited so you can read them yourself. Retrieved 22 September 2026.

Do you need a device for this?

Yes, and it has to be a specific kind. This is the one topic where we will not tell you a phone is enough, because nothing on your phone or your wrist measures blood pressure to a standard any guideline accepts.

The American Heart Association recommends an automatic, cuff-style, upper-arm monitor. Its position on the alternatives is blunt: wrist and finger monitors are not recommended because they give less reliable readings. The 2025 AHA/ACC guideline goes further on the newest category, advising that reliance on cuffless devices, including smartwatches, should be avoided until they demonstrate greater precision.

Two more things about the device itself. It should be validated — the AHA points consumers to validatebp.org, and STRIDE BP maintains an international list. And the cuff has to fit: measure your upper arm, because the wrong cuff size is the single most common measurement error there is.

What an app is for is the other half of the job — holding the readings, averaging them, and turning two months of numbers into something a clinician can read in the ninety seconds they have. That part does not need a sensor.

What a blood pressure log sheet should contain

People call this a blood pressure log, a blood pressure diary, a blood pressure tracker or a home blood pressure chart. They are the same thing, and what a clinician needs from it does not change with the name.

Most people record too little. A clinician reading your log wants to be able to answer "when, under what conditions, and what else was happening" without asking you.

Six columns, and the last one does most of the work. A single spike means nothing on its own and quite a lot next to "slept four hours" or "started new tablet Monday".

If you would rather write on paper, a printable blood pressure log works just as well as an app. The American Heart Association publishes its own printable sheet, My Blood Pressure Log, which records the date and a morning and evening reading for each day. Any layout that captures the fields above will do the job — what matters is that you record both readings from each session and the conditions around them, not which grid you use.

Keep both readings from each session rather than only the better one. The second is usually lower than the first, and that pattern is itself information.

Record your pulse because your monitor already shows it. Resting heart rate over weeks is one of the most interpretable numbers a non-clinician can collect, and a persistent unexplained change in it is worth a conversation.

How to measure so the numbers mean something

The technique is not fussiness. The errors it prevents are larger than the differences people are trying to detect.

The AHA's protocol has four parts, and it is easiest to remember in that shape.

The half hour before. Nothing that raises your heart rate or constricts your vessels: no exercise, no cigarette, no coffee or tea, no alcohol. Thirty minutes is the window the guidance specifies. Go to the loo first — a full bladder is worth about ten points on its own.

The five minutes before. Sit down and stay there, quietly, without talking, for at least five minutes. This is the part people skip, and it is the part that does most of the work.

Your position. Upright in a chair with a back, not perched on a stool or a sofa arm. Both feet on the floor, ankles uncrossed. The arm you are measuring supported on a table, with the cuff level with your heart — if the table is low, put a cushion under your forearm.

The cuff and the reading. Against skin, not over a sleeve, positioned above the elbow crease. Stay quiet while it inflates and don't reach for your phone. Take two readings about a minute apart and write down both. Do it at the same times each day.

Here is why each of those is on the list. The AHA publishes estimated effects for the common errors, and they are not small.

• cuff over clothing — 5–50 mmHg

• full bladder — 10 mmHg

• talking or listening — 10 mmHg

• arm unsupported — 10 mmHg

• cuff too small — 2–10 mmHg

• legs crossed — 2–8 mmHg

• back or feet unsupported — 6.5 mmHg

These are not cumulative, and you will not hit the top of that first range often. But consider that the gap between "normal" and "stage 1 hypertension" is ten points of systolic, and then consider measuring over a jumper with your legs crossed while talking.

That is the whole argument for technique in one line: done carelessly, a home log can manufacture a diagnosis, or hide one.

How often should you check your blood pressure?

How often to check blood pressure depends on why you are checking. For a log you are taking to an appointment, the answer is twice a day for at least a week — not once when you remember. The guideline bodies differ slightly on the detail, so here are all three.

AHA and American Academy of Family Physicians: two readings a minute apart, twice a day, morning and evening, for a minimum of three days and ideally seven.

NICE, in the UK: two consecutive readings at least a minute apart while seated, twice daily, for at least four days and ideally seven — and then discard the first day entirely before averaging.

European Society of Cardiology, 2024: morning readings before breakfast and before taking medication but not immediately on waking, plus evening readings, for a minimum of three days and up to seven; if the three-day average sits close to a threshold, keep going to seven.

Every one of them says the same thing about what to do with the result: average it. A single reading is not usable, and neither is the worst one you saw. If your app or your monitor stores readings, the average is what the consultation is about.

For context on how much data counts as enough in practice: American billing rules for remote self-measured monitoring require at least twelve readings over thirty days, taken two at a time, twice daily.

Why do two readings minutes apart come out different?

This is the most common reason people abandon a log, so it is worth saying plainly: blood pressure is not a fixed property of a person. It moves continuously, and a difference between two readings taken a minute apart is normal rather than a sign that your monitor is broken.

The second reading in a session is usually a little lower than the first. Sitting still for five minutes brings you down; the act of putting on a cuff and waiting for it to inflate brings you up slightly. That is exactly why guidelines ask for two and why they ask you to average rather than pick.

Across the day the swing is larger. Blood pressure typically follows a daily rhythm, which is why every protocol here specifies morning and evening rather than whenever you remember. The ESC is precise about the morning one: before breakfast and before taking your medication, but not in the first moments after waking.

Then there are the things you did. Caffeine, alcohol, a cigarette or exercise in the previous half hour all move the number, which is why the protocol asks you to leave thirty minutes. Pain moves it. A bad night moves it. Being cold moves it. So does the conversation you had on the way to the table.

None of this makes the log unreliable. It makes any single number unreliable, which is a different problem with a simple fix: measure the same way, at the same times, and judge the average over a fortnight rather than the reading in front of you.

If a single alarming number sends you back to measure again immediately, expect the second one to be higher. Anxiety about a reading raises the thing you are trying to read.

What the numbers mean, and why home thresholds differ

This is where most people, and a fair number of articles, go wrong.

The AHA and ACC office categories, unchanged in the 2025 guideline:

Now the part that causes confusion. Home readings are compared against different numbers, because people are generally calmer at their kitchen table than in a consulting room. (See also: white coat and masked hypertension.)

In the United States, ACC/AHA use 130/80 at home as the hypertension threshold — the same figure as their office threshold. In the UK and Europe, NICE and the ESC use 135/85 at home.

That looks like a contradiction and is not. NICE and ESC use 140/90 as their office threshold, and 135/85 is its home equivalent — home values run about 5 mmHg lower. So 135/85 is not a more relaxed version of 130/80; the two pairs sit under different office thresholds entirely.

Practical consequence: check which country's guideline your clinician uses before you decide what your average means. The same log can read as hypertension under one and as elevated-but-not-hypertensive under the other.

White coat and masked hypertension

This is the reason the whole practice exists, and the strongest argument for keeping a log at all.

White coat hypertension is a blood pressure that is high in the consulting room and normal everywhere else. Masked hypertension is the reverse and the more dangerous of the two: normal when a clinician measures it, elevated the rest of the time.

The US Preventive Services Task Force cites international estimates of roughly 8% for white coat and 14% for masked hypertension, with one US study putting masked hypertension at 12.3%. So somewhere around one in five people has a meaningful gap between their office reading and their real one.

The point about masked hypertension is that there is no way to find it in a clinic. The USPSTF puts it plainly: it can only be detected when out-of-office measurements are obtained. And it matters — cardiovascular risk in masked hypertension looks similar to sustained hypertension, roughly double that of people with normal pressure.

Guidelines also use the comparison in the other direction. Under the 2017 ACC/AHA framework, if you are on treatment and your office reading is above target while your home average is at target, that is not a reason to increase your medication.

Do guidelines actually want home readings?

Yes, and more firmly than most people realise.

The USPSTF gives its strongest grade to this: it recommends obtaining blood pressure measurements outside the clinical setting for diagnostic confirmation before starting treatment.

NICE is procedural about it. If your clinic reading falls between 140/90 and 180/120, it says to offer 24-hour ambulatory monitoring to confirm, and home monitoring if ambulatory is unsuitable or not tolerated.

The ESC 2024 guideline recommends out-of-office measurement for diagnosis specifically because it detects white coat and masked hypertension.

The AHA frames home monitoring as confirming the diagnosis and tracking treatment, while being explicit that it does not replace office visits.

So a log is not something you keep in spite of your doctor. It is something several guideline bodies would like you to arrive with.

When a reading is an emergency

Everything above is about patterns over weeks. This part is about right now.

If a reading is suddenly above 180/120, the AHA says to wait at least a minute and measure again. If it is still that high, contact your clinician immediately.

If a reading above 180/120 comes with chest pain, shortness of breath, back pain, numbness or weakness, a change in vision, or difficulty speaking, that is a hypertensive emergency — call emergency services. The AHA's instruction is not to wait and see whether it comes down on its own.

NICE adds that a clinic reading of 180/120 or above alongside certain eye findings or life-threatening symptoms warrants same-day specialist assessment.

What to bring to the appointment

A blood pressure log for a doctor is not the same object as one you keep for yourself. Four things make the difference.

The monitor itself. Both the AHA and the AAFP say to bring it. Your clinician can check it against the office equipment, and the AHA suggests doing that once a year. If the device stores readings, that saves transcription errors as well.

The average, not the extremes. NICE is explicit that the average is what gets used, not individual readings. Arriving with "my average over two weeks was 138/85, from readings twice a day" is a different conversation from "it hit 170 once."

Your notes. Medication changes, when you started or stopped something, poor nights, unusual days. This is what lets a clinician connect a change in the numbers to a cause rather than guessing.

How many readings and over what period. A log of four readings and a log of sixty are different objects, and the clinician needs to know which one they are holding.

What a log cannot do

It cannot diagnose. Hypertension is a clinical diagnosis that takes into account your history, examination and other risk factors, and a home average is one input to it.

It cannot tell you why. Blood pressure moves with sleep, alcohol, salt, pain, stress, illness, medication and the time of day, and the log records the number rather than the cause.

It cannot replace the appointment. Every guideline body here that recommends home monitoring says the same thing in the same breath.

And it cannot fix a measurement problem. A consistent technique error produces a consistent, confident, wrong average — which is worse than no log, because it looks reliable.

How to bring this up with your doctor

Lead with the average and the method: "I measured twice a day, morning and evening, for two weeks, two readings each time. The average was 138/85." That sentence tells a clinician everything they need about how much weight to give it.

Bring the pattern rather than the peak. Mornings consistently higher than evenings is information. One frightening number from a day you ran up the stairs is not.

Say what you changed. If you started a medication, changed the dose, or stopped drinking for a fortnight in the middle of the log, mark where.

If your office reading and your home average disagree substantially, say so directly and ask whether white coat or masked hypertension is worth ruling out. Both are recognised, both are in the guidelines, and out-of-office measurement is how they get identified.

How Welltory fits

Welltory does not measure blood pressure — you need a validated upper-arm cuff for that, as above. What it does is the part after the measurement.

You enter readings in the app, or they arrive through Apple Health, and Welltory keeps them alongside your pulse, HRV, sleep and activity from whatever you already wear. From the blood pressure screen you can generate a doctor report: a PDF covering the last two months, built from a minute and a half of questions about your reason for visiting, your medications and which monitor you use. It arrives by email.

The structure is not invented. Everything this article describes as what a home log should capture — every individual reading with its date and time, both readings from each session, readings separated by time of day, and an average rather than a highlight — is what the report is built from. That is the shape the AHA's home-monitoring guidance asks a log to take, and the form in which NICE says the result should be used.

What is in it maps closely onto what this article says clinicians want: a short summary of the period, then per-metric averages, minimums, maximums, medians and the proportion of readings outside the thresholds, then the full table of blood pressure measurements grouped by morning, day, evening and night, with your own notes next to them. Thresholds follow your region, so a report generated in Europe uses European cut-offs rather than American ones — which, as the section above explains, is not a cosmetic difference.

The report describes what the data shows and the patterns in it. It does not diagnose, does not recommend treatment, and avoids calling a reading normal or abnormal without grounds. This kind of data has a name in clinical practice — patient-generated health data — and it is context for a clinician, not a substitute for examination. Welltory holds no regulatory clearance and the report is not a medical device.

How we made it

Every figure here comes from a named guideline body — the American Heart Association, the American College of Cardiology, the US Preventive Services Task Force, NICE and the European Society of Cardiology — or from a peer-reviewed source those bodies cite, retrieved on 22 September 2026. Where guidelines disagree, as they do on home thresholds and on whether to discard the first day, each position is given separately rather than merged. Where a figure could not be confirmed in a primary source, it was left out.

Made with AI tools, then edited and fact-checked by people.

Data analysis by Jane Smorodnikova — the founder and CEO of Welltory. A recognized tech leader with two Master's degrees and experience at MIT, she has scaled Welltory to over 17 million users.

Written by Tatsiana Yashyna — Deputy COO at Welltory. With a background in medicine and years of working with health data, she translates research and real physiological signals — sleep, stress, heart rate, and hormones — into clear, evidence-based explanations that help people understand what their bodies are telling them.

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