Author:
Kai Knudsen
Updated:
23 December, 2025
This chapter outlines common laboratory tests in healthcare, including reference values, and interpretation for clinical decision-making. This section also describes toxicological thresholds in urine or blood and cut-off levels for drug tests in urine.
- Essential Conversions & Core Formulas
- Weight & Length
- Temperature
- Pressure Conversions
- Volume & Concentration
- Infusion Rate Calculations
- Standard Infusion Strengths (verify local protocols)
- Hemodynamic Calculations
- Oxygenation Formulas
- Local Anesthetic Concentrations
- Local Anesthetic Maximum Doses
- Reference values for normal values
- Toxicological reference values
- Limit values for positive urine tests (drug tests)
Essential Conversions & Core Formulas
Weight & Length
Weight:
• 1 kg = 2.2 lb
• 1 lb = 0.45 kg
Length:
• 1 inch = 2.54 cm
• 1 cm = 0.39 inch
• Quick reference: 6 ft ≈ 183 cm, 5 ft ≈ 152 cm
Temperature
• °F = (°C × 1.8) + 32
• °C = (°F − 32) ÷ 1.8
• Normal: 37 °C (98.6 °F)
• Hypothermia: < 36 °C
Pressure Conversions
• 1 atm = 760 mmHg = 101 kPa
• 1 mmHg = 1.36 cmH₂O
• 1 cmH₂O = 0.74 mmHg
• 1 kPa = 7.5 mmHg
• 1 bar = 750 mmHg
• PEEP 5 cmH₂O ≈ 3.7 mmHg
Volume & Concentration
Volume:
• 1 L = 1000 mL
• 1 mL = 1 cc
Concentration:
• % solution = (% × 10) mg/mL
• 1% = 10 mg/mL
• 0.5% = 5 mg/mL
• 1000 mcg = 1 mg
• 1 mL/kg crystalloid ≈ 1% change in hemoglobin
Infusion Rate Calculations
mcg/kg/min → mL/hr:
Rate = (Dose × Weight (kg) × 60) ÷ Concentration (mcg/mL)
mg/hr → mL/hr:
Rate = Dose (mg/hr) ÷ Concentration (mg/mL)
Units/hr → mL/hr:
Rate = Units/hr ÷ Concentration (units/mL)
Standard Infusion Strengths (verify local protocols)
Vasopressors:
• Epinephrine 1:1000 = 1 mg/mL
• Epinephrine 1:10,000 = 0.1 mg/mL
• Phenylephrine 100 mg/100 mL = 1000 mcg/mL
• Norepinephrine 4 mg/250 mL = 16 mcg/mL
• Vasopressin 20 units/100 mL = 0.2 units/mL
• Dopamine 400 mg/250 mL = 1600 mcg/mL
• Ephedrine 50 mg/10 mL = 5 mg/mL
Hemodynamic Calculations
Mean Arterial Pressure (MAP):
MAP = (SBP + 2 × DBP) ÷ 3
Systemic Vascular Resistance (SVR):
SVR = ((MAP − CVP) ÷ CO) × 80
Normal: 800–1200 dyn·s/cm⁵
Pulmonary Vascular Resistance (PVR):
PVR = ((MPAP − PCWP) ÷ CO) × 80
Normal: 20–120 dyn·s/cm⁵
Cardiac Index (CI):
CI = CO ÷ BSA (Normal: 2.5–4.0 L/min/m²)
Oxygenation Formulas
Oxygen Content (CaO₂):
CaO₂ = (1.34 × Hgb × SaO₂) + (0.003 × PaO₂)
Oxygen Delivery (DO₂):
DO₂ = CO × CaO₂ × 10
Normal: ~520–720 mL/min/m²
A–a Gradient:
A–a = [(FiO₂ × 713) − (PaCO₂ ÷ 0.8)] − PaO₂
Normal: <10–15 mmHg on room air
P/F Ratio:
PaO₂ / FiO₂
ARDS: <300, Severe: <100
Local Anesthetic Concentrations
Lidocaine:
• 0.5% = 5 mg/mL
• 1% = 10 mg/mL
• 2% = 20 mg/mL
Bupivacaine:
• 0.25% = 2.5 mg/mL
• 0.5% = 5 mg/mL
Ropivacaine:
• 0.2% = 2 mg/mL
• 0.5% = 5 mg/mL
Local Anesthetic Maximum Doses
• Lidocaine: 4.5 mg/kg (max 7 mg/kg with epinephrine)
• Bupivacaine: 2.5 mg/kg (max 3 mg/kg with epinephrine)
• Ropivacaine: 3 mg/kg
Monitor for LAST – lipid emulsion 20% as rescue therapy
Reference values for normal values
| Laboratory Analysis | Specimen | Normal Values |
|---|---|---|
| ACT (Activated Clotting Time) | B-: | Normal < 120 sec, fully heparinization > 450 sec, moderate treatment effect: 175-225 sec. |
| Adrenalin | tU-: | 9-101 nmol/d |
| AFP (alfa-phetoprotein) | P-: | 1-5 μg/L |
| Albumin | S-: | 36-45 g/L |
| Aldosteron | P-: | 30-444 nmol/d |
| Alfa-1-antitrypsin | S-: | Men: 0,86-1,75 g/L, Women: 0,94-1,94 g/L |
| ALP | S-: | 0,6-1,8 μkat/L |
| ALT (ALAT) | S-: | 0,15-1,1 μkat/L |
| Ammoniac | P-: | 10-50 μmol/L |
| Amylase | S-: | 0,15 – 1,10 µkat/L (10-65 U/L) |
| Anion Gap | S-: | 6-15 mmol/L |
| Antitrombin | P-: | 0,8-1,2 kIE/L |
| Anti factor Xa | P-: | 0,5-1,0 kIE/L. If <0,1 kIE/L no measurable LMH concentration. If > 1.0 kIE/L reduce the dose. If > 1.5 kIE/L wait 8-12 hours before the next injection. Reduce the dose 25-50%. |
| APTt (Activated Partial Thromboplastin Time) | APTt (Activated Partial Thromboplastin Time) measures factor XII, XI, X, IX, VIII, V, prothrombin and fibrinogen. | 28-42 sec |
| AST (ASAT) | S-: | 0,25-0,75 μkat/L |
| Betaglucan | S-: | Negative sample: <60 pg/mL, limit: 60 pg to 80 pg/mL, positive sample: 80 pg/mL to > 400 |
| Bilirubin conjugated | S-: | < 4 μmol/L |
| Bilirubin total | S-: | 5-25 μmol/L |
| Calcium | S-: | 2,15-2,51 mmol/L |
| Ceruloplasmin | S-: | 0-17 years: 14.0-41.0 mg/dL, and > 18 years: 15.0-30.0 mg/dL |
| CDT (low carbohydrate transferrin): | S-: | < 2,0 % |
| CK (total) | S-: | 0,6-6,7 μkat/L (40-280 U/L) |
| CK MB | S-: | < 5 μg/L |
| COHb | B- | < 2% of tot Hb |
| CRP: | 0,0-5,0 mg/L | |
| Creatinine | S-: | 60-105 μmol/L, 0.5–1.2 mg/dL |
| Creatinine | U-: | Reference values is missing mmol/L |
| Creatinine Clearance | Pt-: | > 65 ml/min, 0.8-1.3 mg/dL |
| Cortisol | S-: | 140-275 nmol/L (daily variations) |
| Cortisol | tU-: | 54-319 nmol/L |
| Chloride | S-: | 97-109 mmol/L |
| Cholesterol | S-: | 3,9-7,8 mmol/L |
| Cholesterol HDL | S-: | 0,8-2,1 mmol/L |
| Cholesterol LDL | S-: | 2,0-5,4 mmol/L |
| DAT - Direct Antiglobulin Test (Coombs Direct Test): | Positive/Negative. Detects antibodies/supplements bound to the erythrocytes. | |
| D-Dimer | P-: | 0,0-0,5 mg/L (< 0,25 mg/L) |
| EVF | Men 40-48 %, Women 34-47 % | |
| EPC | 4,3-5,7 x 1012/L | |
| Ery | Sp-: | 0 x 106/L |
| Fe | S-: | 9-34 μmol/L |
| Ferritin | S-: | 17-235 μg/L |
| Fibrinogen | P-: | 2,0-4,0 g/L |
| Folat | 7,7-25 nmol/L | |
| GFR | Pt-: | > 60 ml/min |
| Glucose | S-: | 4,0-6,3 mmol/L |
| GT | S-: | 0,15-1,9 μkat/L (15-115 U/L) |
| Haptoglobin | P-: | 0-13 years < 1,90 g/L, >13 years 0,24 – 1,90 g/L |
| Haptoglobin | S-: | 0,25-1,9 g/L |
| Hgb (hemoglobin) | Hgb: | Men 13-17 g/dL, Women 11.7-15.3 g/dL |
| HbAc1 | B-: | 4,0-6,0 % |
| INR (PT/INR) | S-: INR = international norm ratio; indicates patient coagulation time / normal coagulation time. PT (INR) is not a test but a way to answer the analysis. PT (prothrombin complex) measures factor II, VII and X. | < 1,1 |
| Lactate | S-: | < 2,4 mmol/L |
| LD, S-: | LD, S-: | 18-70 years < 3,5 µkat/L |
| Lipase | S-: | 13-60 U/L |
| Magnesium | S-: | 0,71-0,94 mmol/L |
| MCH | 27-33 pg | |
| MCV | Men 83-100 fL, Women 80-96 fL | |
| MetHB | B-: | <2% off to Hb |
| Methoxycatecholamines | tU: | 0.5-7.0 nmol/d |
| Myoglobin | P-: | 15-65 μg/L, Men: 25-109 μg/L |
| Noradrenaline | tU: | 62-560 nmol/d |
| NSE, (neuron-specific enolas): | S-: | <12.5 μg/L |
| Osmolality | S-: | 280-300 mosmoles/kg |
| Osmolal Gap | S-: | 10-20 mosmol/L |
| Osmolarity | U-: | 300-900 mosm/kg H2O (> 750 after 8-10 hours of liquid detector) |
| PEth, Phosphatidylethanol | B-: | <0.7 μmol/L |
| Phosphate | S-: | 0,75-1,35 mmol/L |
| Phosfatidylethanol. B-, PEth | B-: | < 0,7 μmol/L |
| Platelets (TPC) | S-: | 150-360 x 109/L |
| Potassium | S-: | 3,6-5,0 mmol/L |
| Potassium | U-: | Reference values is missing mmol/L |
| Potassium daily amount | U-: urine | 30-130 mmol/day |
| PTT (partial thromboplastin time): | P-: | 28-45 seconds |
| ProBNP | S-: | 0-15 pmol/L, < 450 ng/L (>75 years), < 150 ng/L |
| Procalcitonin | S-: | 0,0-0,1 μg/L |
| Renin | P: | 2,8-40 ng/L |
| Reticulocytes | B-: | 30-110 x 109/L |
| Sodium | S-: | 137-145 mmol/L |
| Sodium | U-: | Reference interval missing. Tu-Na (mmol/D)/day volume (L /D) = U-Sodium mmol/L |
| Sodium Daily Amount | U-: | 50-150 mmol/day |
| S-100 B | S-: | > 18 years < 0,11 µg/L |
| Free T4 | S-: | 11-22 pmol/L |
| Free T3 | S-: | 3,1-6,8 pmol/L |
| TIBC | 47-80 μmol/L | |
| Triglycerides | S-: | 0,45-2,60 mmol/L |
| Troponin T | S-: | 0,0-14 ng/L |
| TSH | S-: | 0,3-4,3 mIE/L |
| Urea | S-: | 3,5-8,1 mmol/L |
| Urea | U-: | Ref values missing mmol/L |
| Urea daily amount: | Ref missing 330-580 mmol/day | |
| Vitamine B12: | 150-700 pmol/L | |
| VMA | tU-: | < 34 μmol/24 hours |
| WBC, mono: | Sp- | < 5 x 106/L (leucocytes in cerebrospinal fluid) |
| WBC, poly: | Sp- | < 1 x 106/L |
| WBC white blood cells | 3,5-9 x 109/L |
* Creatinine 1 mg/dL = 88,4 mikromol/L. ** Bilirubin: 1 mg/dL = 17,1 mikromol/L
Toxicological reference values
| Substance | Specimen | Reference Values |
|---|---|---|
| Acetone | S-: | In the case of lighter poisoning, the blood concentration is approximately 2-3 mmol/L. In severe isopropanol poisoning, the acetone concentration may reach a level of about 20 mmol/L. |
| Amatoxin | U-: | In case of suspicion of poisoning with destroying angel, death cap, gallerina marginata or poisonous mushrooms, amatoxin can be determined in urine. Normal limit value is <2 μg/L. |
| Amphetamine | U-: | Responded positively if the sample has a concentration of central stimulants (amphetamine, methamphetamine, MDMA ecstasy) exceeding 300 μg/L (cut off). Reference value: not detectable. |
| Benzodiazepines | U-: | Reference value: Not detectable. Cut off <300 μg/L. |
| Cannabis | U-: | Screening analysis is answered positively if the sample has a concentration of cannabinoids exceeding 50 μg/L (cut off). Reference value: not detectable. |
| Ethanol | S-: | In acute ethanol poisoning, the effect on the CNS dominates. The sensitivity of ethanol shows large individual variations. Generally, the values between 65-90 mmol/L redness and respiratory center effects. At conc. > 100 mmol/l, death may occur by respiratory paralysis (27 mmol/L = 1 promille). |
| Isopropanol | S-: | The general toxicity of isopropanol is greater than ethanol but less than methanol. For lighter poisoning, the blood concentration is <5 mmol/L, whereas severe isopropanol poisoning is present at about 20 mmol/L. |
| Methanol | S-: | Methanol concentration of 15-30 mmol/L represents serious poisoning. Already a concentration of 5-10 mmol/L can cause severe injury if non-active treatment is introduced. |
| Opiates | U-: | Reference value: Not detectable. Cut off < 300 μg/L. |
| Oxazepam | S-: | Therapeutic level: 0.7-4.2 μmol/L. |
| Paracetamol | S-: | Reference value: Not detectable. In case of intoxication, sampling, interpretation of test results and treatment should be in accordance with the Poison Information Center's guidelines. |
Limit values for positive urine tests (drug tests)
Cut Off Values in Urinary Screening Tests
| Substance | ng/ml |
|---|---|
| Amphetamine | 300 |
| Benzodiazepines | 300 |
| Buprenorphine | 10 |
| Fentanyl | 10 |
| Cocaine | 150 |
| MDMA/Ecstasy | 500 |
| Methadone | 300 |
| Methamphetamine | 1000 |
| Opioids | 300 |
| Oxycodone | 100 |
| PPX | 300 |
| TCA (Tricyclic Antidepressive Agents) | 500 |
| THC (Cannabis) | 20/50/150 |
| Tramadol | 100 |
