What low blood pressure really is
Blood pressure is just the push of blood against the walls of the arteries. The top number (systolic) is the push when the heart squeezes; the bottom number (diastolic) is the resting pressure between beats.
We generally call a blood pressure low (hypotension) when it's under about 90/60. But here's the nurse's secret: the number alone never tells the whole story. A small, healthy young adult might live happily at 90/58. What matters is whether there's enough push to perfuse the organs — and whether the patient feels it.
Why it matters: perfusion
"Perfusion" simply means blood actually getting where it needs to go. When pressure drops too low, organs start to starve. That's why you'll see the warning signs show up in the organs that complain first:
- Brain: dizziness, lightheadedness, blurred vision, confusion, fainting
- Kidneys: urine output drops (a quietly important clue)
- Heart & body: a fast, weak pulse as the body tries to compensate; pale, cool, clammy skin; weakness; restlessness
The nurse's role
You are not there to diagnose the cause — you're there to recognize it, assess the patient, act within your scope, and escalate clearly. To do that well, you carry a short mental list of the common causes. We call them the four buckets:
Two honorable mentions worth knowing: orthostatic (positional) drops when someone stands too fast, and allergic reactions (anaphylaxis), which can drop pressure suddenly along with hives or trouble breathing.
Turning the knowledge into hands
Knowing is half of it. The other half is the small, reliable habits that keep your patient safe every single shift.
1. Recheck like a pro
Before you ever sound an alarm, make sure the number is real. A bad reading is one of the most common reasons a "low BP" turns out to be nothing:
- Use the right cuff size — too big reads low, too small reads high.
- Patient resting, arm supported at heart level, feet flat, not talking.
- If it's surprising, recheck — manually, and try the other arm.
2. The ten-second look — every abnormal vital
This is the habit that defines a good nurse. With any off number, lay eyes on the human:
- Make eye contact and talk to them — is their speech the same as yesterday?
- Check their color — pink and warm, or pale and clammy?
- Watch them move — steady, or dizzy when they sit or stand?
- Are they oriented, or newly confused or restless?
3. Orthostatic vitals (the safe way)
When you suspect a positional cause, you can check orthostatics — but safety first:
- Measure BP and pulse lying down, then sitting, then standing, waiting about 1–3 minutes between.
- A meaningful drop is a systolic fall of ≥20 mmHg (or diastolic ≥10), or any new symptoms.
- Guard the patient the whole time — a hand ready, gait belt if needed. If they get dizzy, stop and sit them down.
A simple bedside measure for orthostatic symptoms: if the patient has no trouble swallowing and no gastric-emptying problem, a water bolus — about 480 mL (roughly 16 oz) of plain water — can raise the pressure and ease lightheadedness within minutes. It's an easy, low-risk first step while you finish assessing.
Don't park them flat for long. Lying flat can help in the moment, but keeping a patient supine for prolonged periods can backfire. Some people have coexisting supine hypertension (pressure that climbs when they lie flat) or postprandial hypotension (pressure that dips after meals), so screen for both — reassess in different positions and after eating rather than leaving them flat.
4. Keep them safe & document
- Fall precautions: bed low, call light in reach, ask them not to get up alone.
- Don't leave a symptomatic patient alone to "go tell someone" — bring help to them.
- Chart the number, the position, the symptoms, what you did, and who you told.
Your rep for next clinical day
Pick one patient and run the full habit out loud: recheck with good technique → ten-second look → if needed, a safe orthostatic set → one clean SBAR. One rep builds the instinct.
Show what you know
Five questions. Get 4 of 5 (80%) to complete the unit and unlock Coach Katie's send-off. Every right answer earns Healthy Coins 
and a Drop 💧.
Atta girl. Atta guy. 👏
You didn't just learn a number today. You learned how to look at a person, think through what's happening, and speak up in a way that keeps them safe. That's not a small thing — that's the heart of nursing.
Find one person today — a patient, a classmate, a grandparent, a stranger who looks unsteady — and make their day a little better, a little safer, a little healthier. A kind word. A careful recheck. A "here, let me help you up."