Several common habits and body positions can temporarily raise your blood pressure by 5 to 15 points, enough to push a normal reading into the high range and potentially lead to an unnecessary diagnosis or medication change. Avoiding these mistakes before your next blood pressure check takes minimal effort and can make the difference between an accurate reading and a misleading one.
Skip the Coffee
Caffeine is one of the biggest culprits behind falsely high readings. It can raise systolic pressure (the top number) by 3 to 15 mmHg and diastolic pressure (the bottom number) by 4 to 13 mmHg. Those changes typically begin within 30 minutes of drinking coffee, tea, or an energy drink, peak at one to two hours, and can persist for more than four hours.
A common misconception is that waiting 30 minutes after your last cup is enough. Research published in the journal Blood Pressure Monitoring found that a 30-minute window is not adequate to avoid caffeine’s effects on blood pressure. To be safe, avoid caffeine for at least a few hours before your appointment, or schedule your reading before your morning coffee.
Don’t Smoke or Vape Beforehand
Nicotine stimulates the part of your nervous system that controls your “fight or flight” response, tightening blood vessels and raising both blood pressure and heart rate. These effects from a single cigarette or vaping session can last up to an hour. Wait at least 30 minutes before your reading, though longer is better. The same applies to nicotine patches, gum, or pouches.
Avoid Exercise and Rushing In
Physical activity temporarily raises blood pressure, sometimes significantly. If you walked briskly to the clinic, climbed stairs, or came straight from a workout, your reading will reflect that exertion rather than your resting blood pressure. Wait at least 30 minutes after any moderate to vigorous physical activity before having your blood pressure taken.
Even if you haven’t exercised, rushing into the office and immediately sitting down for a reading can produce an inflated number. Hypertension guidelines have recommended a 3 to 5 minute rest period in a seated position before the first reading for decades. If your provider wraps the cuff around your arm the moment you sit down, ask if you can wait a few minutes first. Research from the AHA suggests that for screening purposes shorter rest times may be acceptable, but if your initial reading comes back at or above 140 systolic, a full 5 minutes of seated rest before re-measuring is important.
Use the Bathroom First
A full bladder is an overlooked source of measurement error. In a study of middle-aged women, holding urine for three or more hours raised systolic blood pressure by an average of 4.2 mmHg and diastolic by 2.8 mmHg compared to readings taken immediately after urination. Four points may not sound like much, but when combined with other small errors on this list, the cumulative effect can meaningfully distort your results. Empty your bladder before your reading.
Don’t Cross Your Legs
This is one of the simplest mistakes to fix, and one of the most impactful. Crossing your legs at the knee during a blood pressure measurement raised systolic pressure by 8 to 10 mmHg and diastolic by about 4 mmHg in patients with hypertension. Even in healthy volunteers, the systolic bump was around 2 to 3 mmHg. The effect is immediate and disappears once you uncross.
Sit with both feet flat on the floor. Your back should be supported against the chair, not leaning forward or perched on the edge of an exam table.
Watch Your Arm Position
Where your arm sits during the reading matters more than most people realize. The gold standard is having your arm supported on a desk or armrest with the middle of the cuff positioned at the level of your heart. A 2024 randomized clinical trial published in JAMA Internal Medicine tested three arm positions and found that letting your arm rest on your lap or hang unsupported at your side both produced higher readings compared to the standard desk-supported position. The reason is simple physics: when the cuff sits lower than your heart, gravity adds pressure to the measurement.
If you’re taking readings at home, set up at a table where you can rest your forearm comfortably. In a clinical setting, speak up if the provider asks you to hold your arm out or rest it in your lap.
Don’t Talk During the Reading
Conversation during measurement, whether you’re speaking or actively listening, raises both systolic and diastolic pressure by about 5 to 6 mmHg. That includes answering questions from your provider, talking on the phone, or even responding to small talk. Stay quiet and still from the moment the cuff begins inflating until the reading is complete. If your provider starts a conversation mid-measurement, it’s fine to politely hold off until the cuff deflates.
Watch Out for Certain Medications
Some over-the-counter medications can raise blood pressure temporarily. Oral decongestants containing pseudoephedrine, found in many cold and sinus products, are the most common offenders. NSAIDs like ibuprofen and naproxen can also contribute to higher readings, especially with regular use. If you’ve taken a decongestant or pain reliever in the hours before your appointment, mention it to your provider so they can factor that into the reading.
Alcohol and Blood Pressure
Alcohol raises blood pressure in the short term, and heavy drinking the night before can leave your readings elevated the next morning. Avoid alcohol for at least 30 minutes before a reading, though if you’re looking for the most accurate baseline, skipping it entirely the day before is a better approach.
Thin Clothing Is Fine
One thing you don’t need to worry about is rolling up a bulky sleeve. Multiple studies have found no significant difference in blood pressure readings taken over a thin sleeve (2 mm or less) compared to bare skin when using standard automated cuffs. A thin shirt or blouse under the cuff won’t affect your results. However, bunching up a thick sweater or jacket above the cuff can create a tourniquet effect that does interfere, so remove heavy outer layers.
Putting It All Together
Each of these factors alone might add only a few points to your reading. But they stack. Cross your legs, skip the bathroom, rush in from a walk, and chat with the nurse during the measurement, and you could easily see a reading that’s 15 to 20 mmHg higher than your true resting blood pressure. That’s the difference between a normal reading and one that looks like it needs treatment.
For the most accurate result: arrive a few minutes early, use the restroom, sit quietly with your feet flat and your back supported, rest your arm on a surface at heart level, and stay still and silent during the reading. If your number comes back high, ask for a second measurement after five minutes of rest before drawing any conclusions.