Taking a manual blood pressure reading on the forearm follows the same basic principles as the standard upper-arm method, but you move the cuff to the forearm and listen over the radial artery at the wrist instead of the brachial artery at the inner elbow. The forearm is a recognized alternative site when the upper arm is inaccessible or when a properly sized cuff simply will not fit, though readings tend to run a few millimeters of mercury higher than upper-arm values. Knowing exactly how to position the cuff, where to place the stethoscope, and how to interpret the numbers you get makes the difference between a useful clinical workaround and a misleading reading.
When Forearm Measurement Makes Sense
The upper arm is the standard site for blood pressure measurement, and for good reason: decades of clinical reference ranges were built around it. But situations arise regularly where you cannot use the upper arm. In emergency and prehospital settings, IV lines, injuries, burns, or casts may occupy both upper arms.1PubMed. Comparison of forearm and upper arm blood pressures In hospitals, patients undergoing dialysis or those with peripherally inserted central catheter lines are often off-limits at the upper arm. Some people have very short upper arms that physically cannot accommodate even a small adult cuff. The European Society of Hypertension has acknowledged this reality, noting that forearm or wrist measurement can be used in clinical practice when a properly sized cuff cannot be applied to the upper arm.2Journal of Hypertension. Recommendations for blood pressure measurement in large arms in research and clinical practice
Obesity is another common reason. When the upper arm has a large circumference and a conical shape that tapers sharply toward the shoulder, even a large or thigh-sized cuff may not stay in place properly. A conically shaped arm can cause the cuff to slide or fit unevenly, potentially introducing errors as large as 10 mmHg.3PubMed Central. Cuff challenges in blood pressure measurement In these cases, the forearm’s more cylindrical shape can actually provide a better surface for the cuff to grip.
Step-by-Step Technique
The process is straightforward once you understand the key differences from a standard upper-arm measurement. You will need a manual sphygmomanometer (the inflatable cuff attached to a pressure gauge) and a stethoscope.
- Seat the patient: Have them sit comfortably with their forearm resting on a flat surface at heart level. If they are lying down, the arm should rest at their side, supported so it does not dangle.
- Measure the forearm: Wrap a tape measure around the midpoint of the forearm, roughly halfway between the elbow crease and the wrist. This circumference determines which cuff size you need.
- Wrap the cuff: Place the bladder of the cuff around the mid-forearm. The lower edge of the cuff should sit about two to three centimeters above the wrist crease, leaving room for the stethoscope. The cuff should be snug but not tight, with about one finger’s width of space beneath it.
- Locate the radial artery: This is the pulse you feel at the thumb side of the inner wrist. Place two fingers over it to confirm the location before positioning your stethoscope.
- Place the stethoscope: Set the bell or diaphragm of the stethoscope directly over the radial artery, just below the lower edge of the cuff. You are listening here instead of at the elbow because the brachial artery is now under the cuff rather than below it.
- Inflate and listen: Inflate the cuff to about 30 mmHg above the point where you can no longer feel the radial pulse. Then slowly deflate at a rate of roughly 2 to 3 mmHg per second. The first clear tapping sound (Korotkoff sound) marks your systolic pressure. The point where those sounds disappear marks your diastolic pressure.
One practical tip that often gets overlooked: make sure the arm is truly at heart level. When the forearm hangs below the heart, gravity adds pressure to the reading. When it sits above the heart, the reading drops. This effect is the same as with upper-arm measurement, but because you are already working with an alternative site that introduces some inherent variability, keeping the forearm level with the heart becomes even more important.
Choosing the Right Cuff Size
Cuff fit is the single biggest source of error in any blood pressure measurement, and it matters just as much on the forearm. The bladder inside the cuff (the inflatable part, not the outer fabric) should ideally cover about 40% of the circumference of the forearm and roughly 80% of its length. Research specifically examining cuff-width-to-circumference ratios on the forearm confirmed that these proportions matter for getting a reliable reading.4Acta Paulista de Enfermagem. Arm and forearm blood pressure measurements as a function of cuff width
Most forearms are smaller than most upper arms, which means a standard adult cuff is often appropriate for the forearm even in people who would need a large adult cuff on their upper arm. But do not assume. If you are measuring someone with muscular or larger forearms, you may still need to size up. A cuff that is too narrow will give you a falsely high reading. A cuff that is too wide will give you a falsely low one. The same rules that apply to the upper arm apply here, and ignoring them is the fastest way to get a number that is off by a clinically meaningful amount.
How Forearm Readings Compare to Upper-Arm Readings
The honest reality is that forearm blood pressure does not perfectly match upper-arm blood pressure. Multiple studies have looked at this question from different angles, and the general finding is consistent: forearm readings tend to run slightly higher, especially for systolic pressure.
A study of adult emergency department patients found that forearm measurement overestimated systolic pressure by an average of about 2 mmHg and diastolic by about 3 mmHg compared to upper-arm readings.5International Journal of Nursing Studies. Comparison study of upper arm and forearm non-invasive blood pressures in adult Emergency Department patients Those averages sound small, but the individual variation was much wider, with limits of agreement stretching to roughly plus or minus 19 mmHg for systolic readings. That means some individual patients showed forearm readings almost 20 mmHg above or below their upper-arm readings, even when the group average difference was small.
A separate study in obese patients confirmed the overestimation pattern, finding that forearm readings with a standard cuff were significantly higher than upper-arm readings taken with an appropriately sized cuff.6PubMed. Blood pressure measurement in obese patients: comparison between upper arm and forearm measurements This is a consistent theme in the literature and something to keep in mind whenever you interpret a forearm reading.
The practical takeaway: a forearm blood pressure gives you a useful ballpark, especially for tracking trends over time, but the number is not directly interchangeable with an upper-arm reading. If you get 138/88 on the forearm, the upper-arm value could plausibly be a few points lower. Do not use a single forearm reading to make a definitive diagnosis of hypertension.
Why Forearm Readings Run Higher
The forearm is anatomically different from the upper arm in ways that affect how pressure transmits through the cuff. The forearm contains two bones (the radius and ulna) rather than one, and these rigid structures sit close beneath the skin and muscle. When the cuff inflates, it cannot compress the tissue as evenly as it does on the upper arm, where a single bone (the humerus) sits deeper inside a more uniform cylinder of soft tissue. The result is that higher cuff pressure is needed to fully occlude the radial and ulnar arteries, which shows up on your gauge as a higher systolic reading.
The arteries in the forearm are also smaller and more peripheral than the brachial artery. Blood pressure naturally amplifies as it moves toward the periphery because of the way arterial walls stiffen and branch. This is the same reason why a blood pressure taken at the ankle typically reads higher than one at the upper arm. The forearm sits partway along that gradient, so you tend to see a modest bump.
The Obesity Exception
Here is where the evidence gets genuinely interesting. While forearm readings usually overestimate relative to a properly fitted upper-arm cuff, “properly fitted” is doing a lot of work in that sentence. In severely obese patients, getting a properly fitted upper-arm cuff is often the problem. If the only cuff you can get on the upper arm is too small or sits on a cone-shaped arm, that upper-arm reading might itself be falsely elevated.
A validation study in severely obese patients compared forearm blood pressure to intra-arterial readings (the gold standard, measured directly inside an artery with a catheter). The forearm method overestimated systolic pressure by about 6 mmHg and underestimated diastolic by about 2 mmHg compared to the intra-arterial standard. Meanwhile, the upper-arm cuff underestimated systolic by about 8 mmHg and overestimated diastolic by about 9 mmHg. The overall magnitude of error was actually smaller with the forearm approach.7PubMed. Blood pressure assessment in severe obesity: validation of a forearm approach In other words, for this specific population, the forearm was the more accurate site.
A follow-up study tested different body positions and found that forearm systolic readings agreed best with the gold standard when patients were lying flat on their backs or sitting in a reclined position with the arm pointing downward. Correlations between forearm and intra-arterial measurements were strong, around 0.95 for systolic pressure.8PubMed. Blood Pressure Measurement in Severely Obese Patients: Validation of the Forearm Approach in Different Arm Positions The researchers concluded that this method is a viable option in clinical settings where upper-arm measurement is challenging in severe obesity.
If you work with patients whose upper-arm circumference exceeds the range of your largest cuff, the forearm is not just a second-best fallback. It may actually give you a more reliable number than forcing a too-small cuff onto the upper arm.
Position Matters More Than You Think
Arm position has an outsized effect on forearm readings. The validation study just mentioned found that the position of the arm relative to the body changed the agreement between the forearm reading and the gold standard substantially. Lying supine with the arm resting naturally at the side consistently produced the best results. A semi-reclined position with the arm hanging downward was the next best option.8PubMed. Blood Pressure Measurement in Severely Obese Patients: Validation of the Forearm Approach in Different Arm Positions
When patients sat upright with their forearm resting on a table, agreement worsened somewhat. And when the arm was elevated above heart level, readings dropped, introducing additional error in the opposite direction. The simple rule: keep the forearm at or slightly below heart level and support it so the patient is not actively holding it in position (muscle tension affects the reading). If the patient is in a hospital bed, adjusting the bed to a slight recline and letting the arm rest at the side is the easiest way to hit the sweet spot.
Using Palpation Instead of Auscultation
If the environment is too noisy to hear Korotkoff sounds clearly, or if you are struggling to pick up sounds over the radial artery, you can fall back to the palpation method. This means feeling for the radial pulse at the wrist instead of listening with a stethoscope. Inflate the cuff until the pulse disappears, then slowly deflate. The pressure on the gauge at the moment you first feel the pulse return is your systolic reading.
The palpation approach has a significant limitation: it only gives you a systolic value. You cannot reliably detect the diastolic endpoint by touch. Research has confirmed that palpation of the radial artery provides a reasonable estimate of systolic blood pressure, particularly in settings where auscultation is difficult.9Journal of Hypertension. Reliability of palpation of the radial artery compared with auscultation of the brachial artery in measuring SBP This makes it a practical field technique for quick assessments, even if it gives you incomplete data. In a prehospital or triage situation, knowing systolic pressure alone is often enough to guide immediate decisions.
Forearm Blood Pressure in Children
The forearm method does not translate well to pediatric patients. A study that compared forearm and upper-arm readings in children found that, while the two sites correlated reasonably well, forearm readings were consistently about 3 mmHg higher.10PubMed Central. Is it reliable to measure the forearm blood pressure in children? More concerning were findings from studies in anesthetized children, which showed much wider disagreement. In one study, the systolic difference between arm and forearm fell within a 10% range in only about 63% of measurements, meaning over a third of readings were off by more than 10%.11Journal of Clinical Anesthesia. Inconsistency between simultaneous blood pressure measurements in the arm, forearm, and leg in anesthetized children
A separate pediatric study concluded bluntly that the forearm should not be used interchangeably with the upper arm in anesthetized healthy children, and that future use would require cuffs specifically designed and validated for the pediatric forearm.12PubMed. Suitability of the forearm for non-invasive blood pressure measurement in children The pediatric forearm is proportionally different from an adult’s: shorter, more tapered, and with thinner soft tissue. Standard cuffs, even small ones, do not conform to it the same way. If you must use a forearm reading in a child, treat it as a rough estimate and flag in your documentation that it was obtained from an alternative site.
Documenting and Communicating Forearm Readings
Any time you take blood pressure from the forearm, note it explicitly. Writing “BP 142/86, R forearm” rather than just “BP 142/86” prevents the next clinician from comparing that number directly to an upper-arm baseline and mistakenly concluding the patient’s pressure has risen. If you are monitoring trends, try to use the same site and the same arm consistently. Switching between upper arm and forearm between visits introduces noise that can obscure real changes.
In documentation, it also helps to note why the forearm was used. “Upper arm inaccessible due to bilateral IV access” or “upper arm circumference exceeds cuff range” gives future readers context for interpreting the value. Some electronic health record systems have a specific field for measurement site. If yours does, use it. If it does not, a free-text note is worth the extra ten seconds.
Common Mistakes to Avoid
A few errors come up repeatedly when people take forearm blood pressures, and most of them are easily preventable.
- Listening at the elbow: On the upper arm, you place the stethoscope over the brachial artery at the antecubital fossa (the inner elbow). When the cuff is on the forearm, the brachial artery is above the cuff and no longer useful. You need to listen over the radial artery at the wrist. Placing the stethoscope in the wrong spot is the most common reason people get no sound at all and assume the technique does not work.
- Using a cuff that is too large: People sometimes grab a large adult cuff thinking bigger is safer. On the forearm, an oversized bladder wraps too far around the circumference and gives a falsely low reading, which is the opposite of what most clinicians expect from a forearm measurement.
- Letting the arm dangle: If the forearm hangs off the side of a chair or bed, it sits below heart level, and gravity inflates the reading. Support the forearm on a surface at the level of the heart.
- Deflating too fast: Because Korotkoff sounds can be quieter over the radial artery than over the brachial, a fast deflation rate makes it easy to miss the first and last sounds. Stick to 2 to 3 mmHg per second, and err on the side of slow if the sounds are faint.
When to Avoid the Forearm Entirely
The forearm is not an appropriate site in every situation. If the patient has an arteriovenous fistula for dialysis in that arm, avoid the entire limb. If there is lymphedema, cellulitis, or a recent injury to the forearm, choose a different site. Patients with significant peripheral vascular disease may have unreliable forearm readings because atherosclerosis in the smaller arteries of the forearm can artificially elevate systolic pressure even further. In these patients, a thigh cuff on the upper arm (if it fits) or direct arterial monitoring is preferable.
For patients who are critically ill and hemodynamically unstable, no non-invasive site is ideal. The oscillometric and auscultatory methods both become less reliable as blood pressure drops. If a forearm reading is the only option you have, it can still guide resuscitation efforts, but confirm with invasive monitoring as soon as possible.