What is normal blood pressure by age?

For adults, normal blood pressure is below 120/80 mmHg regardless of age. AHA categories: Elevated 120-129/<80, Stage 1 Hypertension 130-139/80-89, Stage 2 ≥140/≥90, Hypertensive Crisis ≥180/≥120. Children have lower normal ranges (e.g., a 10-year-old: ~100/65 mmHg). Always consult your doctor for personalized guidance.

What blood type is the universal donor?

O-negative (O−) is the universal red blood cell donor — it can be transfused to patients of any blood type. AB-positive (AB+) is the universal recipient. AB plasma donors can donate plasma to all blood types.

What is the Mosteller formula for Body Surface Area?

Mosteller formula: BSA (m²) = √(height(cm) × weight(kg) / 3600). Average adult BSA is ~1.7 m². BSA is used for chemotherapy dosing, burn assessment, and GFR normalization.

🩺 Health & WellnessLast updated May 3, 2026

Blood Health & Vitals Guide 2026: Blood Pressure, Blood Type, BAC & Key Body Metrics

Clinical-grade explanations of your most important health numbers — with free calculators

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Free Calculators

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BP Categories

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Blood Types

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Key Takeaways

Normal blood pressure is below 120/80 mmHg. Elevated: 120–129/<80. Hypertension Stage 1: 130–139/80–89. Stage 2: ≥140/≥90. Hypertensive Crisis: ≥180/≥120 (seek emergency care immediately).
Systolic pressure (top number) is the force during heartbeats; diastolic (bottom) is the force between beats. Mean Arterial Pressure (MAP) = (Systolic + 2 × Diastolic) / 3 — normal range 70–100 mmHg.
The DASH diet (low sodium, high potassium) can reduce blood pressure by 8–14 mmHg — as effective as some medications for Stage 1 hypertension.
There are 8 main blood types (A+, A-, B+, B-, O+, O-, AB+, AB-). O- is the universal red cell donor; AB+ is the universal recipient. AB plasma donors can donate to all types.
Rh factor incompatibility during pregnancy (Rh- mother, Rh+ baby) can cause hemolytic disease in subsequent pregnancies. RhoGAM injection at 28 weeks and delivery prevents sensitization.
BAC = (grams of alcohol consumed) / (body weight in grams × Widmark factor r) − (0.015 × hours since first drink). r = 0.68 for men, 0.55 for women. US legal driving limit: 0.08%.
Body Surface Area (BSA) using Mosteller formula: BSA (m²) = √(height(cm) × weight(kg) / 3600). Used for chemotherapy dosing, IV drug dosing, and burn assessment (Rule of Nines for %TBSA).
Normal resting heart rate: 60–100 bpm (adults). Athletes may have 40–60 bpm. Normal SpO2 (blood oxygen saturation): 95–100%. Below 90% requires immediate medical attention.
Healthy LDL cholesterol: below 100 mg/dL (optimal), 100–129 near optimal, 130–159 borderline high, 160+ high. HDL above 60 mg/dL is protective; below 40 mg/dL (men) / 50 (women) is a risk factor.
HbA1c reflects average blood sugar over 3 months. Normal: below 5.7%. Prediabetes: 5.7–6.4%. Diabetes: 6.5%+. Each 1% reduction in HbA1c lowers risk of diabetic complications by ~14–21%.

Your blood health and vital signs are the most direct window into overall wellness — and small deviations can signal serious conditions years before symptoms appear. This 2026 guide, grounded in American Heart Association guidelines, Red Cross blood type standards, and NIAAA alcohol metabolism data, covers every key metric from systolic/diastolic blood pressure to ABO blood typing, BAC, body surface area, heart rate zones, SpO2, cholesterol, and HbA1c — with free calculators including our blood pressure calculator, blood type compatibility calculator, BAC calculator, and BSA calculator.

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Blood Pressure Categories: The Complete AHA Chart

The American Heart Association defines five blood pressure categories: Normal (<120/<80 mmHg) — maintain with healthy lifestyle. Elevated (120–129/<80 mmHg) — lifestyle changes recommended; no medication yet. Hypertension Stage 1 (130–139/80–89 mmHg) — lifestyle changes + possible medication depending on cardiovascular risk. Hypertension Stage 2 (≥140/≥90 mmHg) — lifestyle changes plus medication. Hypertensive Crisis (≥180/≥120 mmHg) — seek emergency care immediately, especially with chest pain, shortness of breath, or neurological symptoms. Low blood pressure (hypotension): below 90/60 mmHg — can cause dizziness and fainting. Home monitoring tip: Measure in the morning before medication, sit quietly for 5 minutes, use the same arm each time, take 2–3 readings and average them. Use our blood pressure calculator to interpret your readings.

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Systolic vs Diastolic: What the Numbers Mean

Systolic pressure (top number): the peak pressure when your heart contracts and pumps blood into the aorta. It reflects cardiac output and arterial compliance. Diastolic pressure (bottom number): the minimum pressure when the heart relaxes and refills between beats. It reflects peripheral vascular resistance. Mean Arterial Pressure (MAP) = (Systolic + 2 × Diastolic) / 3 — represents the average pressure throughout one cardiac cycle. Normal MAP: 70–100 mmHg. Below 60 mmHg impairs organ perfusion. Pulse pressure = Systolic − Diastolic. Normal: 40–60 mmHg. Widened pulse pressure (>60) may indicate aortic regurgitation or arterial stiffness; narrowed (<25) may suggest cardiac tamponade or heart failure. Isolated systolic hypertension (systolic ≥140, diastolic <90) is the most common form in adults over 60 and is a major stroke risk factor.

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How to Lower Blood Pressure Naturally: Evidence-Based Strategies

Clinical evidence supports these non-pharmacological interventions: (1) DASH diet (Dietary Approaches to Stop Hypertension): emphasizes fruits, vegetables, whole grains, lean protein, low sodium (<2,300 mg/day, ideally <1,500 mg). Can reduce BP by 8–14 mmHg. (2) Regular aerobic exercise: 150 minutes/week of moderate activity (brisk walking, swimming, cycling) reduces BP by 4–11 mmHg. Resistance training adds further benefit. (3) Weight reduction: losing 5–10 kg reduces systolic BP by 5–10 mmHg. (4) Alcohol moderation: maximum 1 drink/day (women), 2/day (men). Excess alcohol raises BP directly. (5) Quit smoking: nicotine causes immediate BP spikes and long-term arterial stiffness. (6) Potassium intake: 3,500–5,000 mg/day (bananas, sweet potatoes, beans) counteracts sodium. (7) Stress management: chronic stress activates the sympathetic nervous system; regular mindfulness, deep breathing, and yoga help. (8) Sleep: 7–8 hours; sleep apnea treatment can reduce BP significantly.

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ABO Blood Type System: Antigens, Antibodies & Types Explained

The ABO system is based on the presence or absence of A and B antigens on red blood cells, and the corresponding antibodies in plasma. Type A: A antigens, anti-B antibodies. Type B: B antigens, anti-A antibodies. Type AB: both A and B antigens, no ABO antibodies (universal plasma donor for plasma transfusions). Type O: no A/B antigens, both anti-A and anti-B antibodies (universal red cell donor). Blood types are inherited — determined by alleles from each parent. The A and B alleles are codominant; O is recessive. In the US: ~44% are O+, ~42% A+, ~10% B+, ~4% AB+ — O is the most common type worldwide. Blood typing is critical for transfusion compatibility, organ transplant matching, and forensic medicine.

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Rh Factor, Pregnancy & Hemolytic Disease

The Rh factor (D antigen) divides blood types into positive (+) and negative (−). About 85% of people are Rh+. Rh incompatibility in pregnancy: If an Rh− mother carries an Rh+ baby, small amounts of baby’s blood can enter the mother’s circulation (during delivery, miscarriage, amniocentesis, or trauma). The mother’s immune system produces anti-D antibodies. Hemolytic Disease of the Newborn (HDN): In a subsequent Rh+ pregnancy, these antibodies cross the placenta and destroy the baby’s red blood cells — potentially causing severe anemia, jaundice, hydrops fetalis, or stillbirth. Prevention: RhoGAM (anti-D immunoglobulin) injection at 28 weeks gestation and within 72 hours of delivery neutralizes any Rh+ cells before sensitization occurs. All Rh− pregnant women should receive Rh screening and RhoGAM as indicated.

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Blood Type Donation Compatibility Chart

Red blood cell donation (most common): O− → All types (universal donor). O+ → O+, A+, B+, AB+. A− → A−, A+, AB−, AB+. A+ → A+, AB+. B− → B−, B+, AB−, AB+. B+ → B+, AB+. AB− → AB−, AB+. AB+ → AB+ only. Plasma donation: AB plasma is the universal plasma donor. O plasma can only go to O recipients. Platelet donation: All types can donate to all types (cross-matching less critical). Blood demand facts: Someone in the US needs blood every 2 seconds. O+ is the most transfused type (most common type + universal for Rh+ patients). O− is reserved for emergencies when blood type is unknown. Use our blood type calculator to check your specific compatibility.

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Blood Alcohol Content (BAC): Calculation, Legal Limits & Metabolism

Widmark formula: BAC (%) = [Grams of alcohol / (Body weight (g) × r)] − (0.015 × Hours). Widmark factor r: 0.68 (men), 0.55 (women). One standard US drink = 14g pure alcohol. Legal limits (blood alcohol): USA: 0.08% (most states); some states 0.05% commercial drivers. UK: 0.08%. EU: 0.05% (many countries). Canada: 0.08% (legal) / 0.05% (warn range). Physiological effects by BAC: 0.02–0.05%: relaxation, mild euphoria. 0.05–0.08%: impaired judgment, reduced coordination. 0.08–0.15%: poor reaction time, impaired balance. 0.15–0.25%: confusion, nausea, possible blackout. Above 0.25%: life-threatening. Elimination rate: approximately 0.015% per hour (Widmark constant) for most people — cannot be sped up by coffee, water, or food. Use our BAC calculator for personalized estimates.

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Body Surface Area (BSA): Formulas, Calculation & Clinical Uses

BSA formulas: Mosteller (most common): BSA = √(height(cm) × weight(kg) / 3600). DuBois & DuBois: BSA = 0.007184 × height(cm)^0.725 × weight(kg)^0.425. Haycock: BSA = 0.024265 × height(cm)^0.3964 × weight(kg)^0.5378. Average adult BSA: ~1.7 m² (men ~1.9 m², women ~1.6 m²). Clinical applications: (1) Chemotherapy dosing: doses expressed in mg/m² to normalize for body size and reduce toxicity variation. (2) Burn assessment: Rule of Nines — each body area equals 9% of BSA (head 9%, each arm 9%, each leg 18%, torso front 18%, torso back 18%). (3) Cardiac index: cardiac output (L/min) / BSA (m²) — normal 2.5–4.0 L/min/m². (4) GFR normalization: normalized to 1.73 m² for kidney function comparison. Use our BSA calculator for all formulas.

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Resting Heart Rate, SpO2 & Key Vital Signs

Heart rate (HR) normal ranges: Adults: 60–100 bpm. Well-trained athletes: 40–60 bpm. Children (1–10 years): 70–120 bpm. Newborns: 120–160 bpm. Bradycardia: <60 bpm (may be normal in athletes). Tachycardia: >100 bpm. Maximum heart rate estimate: 220 − age. Target exercise zones: 50–60% (moderate), 60–70% (fat burn), 70–85% (aerobic). Blood oxygen saturation (SpO2): Normal: 95–100%. Acceptable: 90–94%. Emergency: <90%. Normal body temperature: Oral: 97.8–100.4°F (36.6–38.0°C). Rectal: ~1°F higher. Axillary: ~1°F lower. Fever: >100.4°F (38°C). Hypothermia: <95°F (35°C). Respiratory rate: Adults: 12–20 breaths/minute. >24 may indicate respiratory distress. Quick vitals check: Blood pressure + heart rate + SpO2 + temperature = basic vitals panel in any clinical assessment.

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Cholesterol, LDL/HDL & HbA1c: Understanding Your Lab Results

Total cholesterol targets (mg/dL): Desirable: <200. Borderline high: 200–239. High: ≥240. LDL (“bad”): Optimal: <100; Near optimal: 100–129; Borderline high: 130–159; High: 160–189; Very high: ≥190. HDL (“good”): Low risk: ≥60; Average: 40–59; High risk: <40 (men) / <50 (women). Triglycerides: Normal: <150; Borderline: 150–199; High: 200–499; Very high: ≥500. HbA1c (glycated hemoglobin): Normal: <5.7%. Prediabetes: 5.7–6.4%. Diabetes: ≥6.5%. Conversion: eAG (mg/dL) = (28.7 × HbA1c) − 46.7. Statins reduce LDL by 30–50%. Exercise raises HDL by 3–6%. Mediterranean diet reduces cardiovascular risk by ~25%. Annual fasting lipid panel recommended for adults ≥20 years; more frequently if abnormal.

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HbA1c ranges, eAG conversion, and what each level means for prediabetes and diabetes management.

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Frequently Asked Questions

What is a normal blood pressure reading by age?

For adults: Normal is below 120/80 mmHg regardless of age, though BP naturally tends to rise with age. Elevated: 120–129 systolic and less than 80 diastolic. Stage 1 Hypertension: 130–139/80–89 mmHg. Stage 2 Hypertension: 140+/90+ mmHg. Hypertensive Crisis: 180+/120+ (emergency). Children and teens have lower normal ranges: for a 10-year-old, normal is around 100/65; for a 16-year-old, around 117/77. Always check with your doctor for age-specific ranges.

What does systolic vs diastolic blood pressure mean?

Systolic pressure (the top number) measures the pressure in your arteries when your heart beats and pumps blood. Diastolic (the bottom number) measures pressure when your heart rests between beats. Mean Arterial Pressure (MAP) = (Systolic + 2 × Diastolic) / 3 — a MAP above 60 mmHg is needed to perfuse vital organs. Pulse pressure = Systolic − Diastolic; a pulse pressure above 60 mmHg may indicate arterial stiffness.

How can I lower blood pressure naturally?

Evidence-based lifestyle changes: (1) DASH diet: rich in fruits, vegetables, whole grains, low sodium (below 2,300 mg/day) — can reduce BP by 8–14 mmHg. (2) Exercise: 150 minutes/week of moderate aerobic activity — reduces BP by 4ₓ11 mmHg. (3) Weight loss: each 1 kg lost reduces BP by ~1 mmHg. (4) Limit alcohol: no more than 1 drink/day (women) or 2 (men). (5) Quit smoking: each cigarette causes a temporary BP spike. (6) Stress management: deep breathing, meditation, yoga. Consult your doctor before making major changes.

What blood type can I donate to and receive from?

Donation compatibility by red blood cells: O- can donate to all (universal donor); O+ to O+, A+, B+, AB+; A- to A- and AB-; A+ to A+ and AB+; B- to B- and AB-; B+ to B+ and AB+; AB- to AB- and AB+; AB+ only to AB+. For receiving: AB+ can receive from all (universal recipient); O- can only receive O-. Always confirm with your blood bank before any transfusion.

What is the Rh factor and why does it matter in pregnancy?

The Rh factor (Rhesus factor) is an antigen on red blood cells. About 85% of people are Rh-positive (have the antigen); 15% are Rh-negative. In pregnancy, if the mother is Rh-negative and the baby is Rh-positive, the mother’s immune system can develop antibodies against Rh+ blood after exposure (typically during delivery or miscarriage). In subsequent Rh+ pregnancies, these antibodies can attack the baby’s red blood cells, causing hemolytic disease of the newborn (HDN). RhoGAM (anti-D immunoglobulin) injection at 28 weeks gestation and within 72 hours of delivery prevents sensitization.

How do you calculate BAC accurately?

The Widmark formula: BAC (%) = [grams of alcohol / (body weight (g) × r)] − (0.015 × hours elapsed). Widmark factor r = 0.68 for men, 0.55 for women (reflects water content). One standard US drink = 14g of pure alcohol (12 oz regular beer, 5 oz wine at 12%, or 1.5 oz spirits at 40%). Example: 70 kg male, 3 drinks, 1 hour elapsed: BAC = [42 / (70,000 × 0.68)] − 0.015 = 0.0882 − 0.015 = 0.073%. Use our BAC calculator for personalized estimates — these are approximations; individual metabolism varies significantly.

How is Body Surface Area calculated and used?

Most common formula — Mosteller: BSA (m²) = √[height(cm) × weight(kg) / 3600]. DuBois formula: BSA = 0.007184 × height(cm)^0.725 × weight(kg)^0.425. Average BSA: 1.7 m² for adults. Clinical uses: (1) Chemotherapy dosing — doses in mg/m² to minimize toxicity variation. (2) Burn assessment — Rule of Nines calculates %Total Body Surface Area burned. (3) Physiological measurements (cardiac index = cardiac output / BSA). (4) Kidney function assessment (GFR normalized to 1.73 m²).

What is normal blood oxygen saturation (SpO2)?

Normal SpO2 (measured with a pulse oximeter) is 95–100%. 90–94% is considered low and warrants medical evaluation. Below 90% is a medical emergency — oxygen supplementation required. During sleep, SpO2 may briefly dip to 90–94% in healthy individuals. People with COPD or chronic lung disease may have baseline SpO2 of 88–92%. High altitude reduces SpO2 (at 8,000 ft, SpO2 around 92–95% is typical). Poor probe positioning (nail polish, cold extremities) can give false low readings.

What do LDL and HDL cholesterol numbers mean?

LDL (“bad” cholesterol) builds up in artery walls. Target levels: below 100 mg/dL (optimal); 100–129 near optimal; 130–159 borderline high; 160–189 high; 190+ very high. HDL (“good” cholesterol) helps remove LDL from blood vessels. Below 40 mg/dL (men) / 50 mg/dL (women) is low — a risk factor. Above 60 mg/dL is protective. Total cholesterol below 200 mg/dL is desirable. Triglycerides: below 150 mg/dL normal. Statins, exercise, and dietary changes can improve all four markers.

What is HbA1c and what are normal levels?

HbA1c (glycated hemoglobin) measures the percentage of hemoglobin coated with glucose — reflecting average blood sugar over 2–3 months. Normal: below 5.7%. Prediabetes: 5.7–6.4% (eAG 117–137 mg/dL). Diabetes: 6.5%+ (eAG 140+ mg/dL). ADA target for people with diabetes: below 7% (eAG below 154 mg/dL). Each 1% increase in HbA1c roughly corresponds to +35 mg/dL average blood glucose. Tested every 3–6 months for people with diabetes; annually for those with prediabetes.

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