What is the conversion factor between mg/dL and mmol/L?
Blood sugar (glucose) conversion: 1 mmol/L = 18.016 mg/dL; 1 mg/dL = 0.0555 mmol/L. Clinically, the simplified factor of 18 is commonly used (mmol/L × 18 = mg/dL). This tool uses the more precise 18.016 (calculated from glucose molecular formula C₆H₁₂O₆ molecular weight 180.156 g/mol), with error less than 0.1%, fully meeting clinical recording accuracy requirements.
Why do China/USA use mg/dL while Europe/Canada/UK use mmol/L?
mg/dL (milligrams per deciliter) is a traditional mass concentration unit originating from early clinical chemistry measurement by mass; mmol/L (millimoles per liter) is the SI (International System of Units) amount-of-substance concentration unit recommended by IUPAC (International Union of Pure and Applied Chemistry), reflecting molecular count. The USA, China, Japan, India, France (alternating use) and others still use mg/dL; the UK, Canada, Australia, and most continental European countries use mmol/L. Different glucometers default to different units; imported/overseas-purchased glucometers often require manual conversion.
What is the normal blood sugar range? What are the hypoglycemia and hyperglycemia thresholds?
General clinical reference (fasting venous plasma glucose): Normal fasting blood sugar 3.9–6.1 mmol/L (70–110 mg/dL); Impaired Fasting Glucose (IFG) 6.1–7.0 mmol/L (110–126 mg/dL); Diabetes diagnostic threshold fasting ≥7.0 mmol/L (≥126 mg/dL) or 2-hour postprandial/OGTT ≥11.1 mmol/L (≥200 mg/dL); Hypoglycemia alert value <3.9 mmol/L (<70 mg/dL), severe hypoglycemia <2.8 mmol/L (<50 mg/dL). ⚠️ Please rely on a physician's judgment for diagnosis - this tool is for unit conversion reference only.
Can this converter be used for cholesterol, uric acid, or triglycerides?
No. The mg/dL to mmol/L conversion factor is strongly dependent on the molar mass (molecular weight) of the substance - each chemical has a different factor: cholesterol factor is 38.67 (MW 386.65), triglycerides is 88.57 (MW 885.7), uric acid is 16.81, creatinine is 88.4, and HbA1c uses a completely different system (percentage or mmol/mol). This tool is specifically for glucose (MW 180.16, factor 18.016). Misapplication to other analytes will produce completely incorrect results.
What if my home glucometer shows different units than the hospital lab report?
Many imported/overseas-purchased glucometers (e.g., US, Japanese models) default to mg/dL, while domestic hospital lab reports usually list mmol/L or use mmol/L exclusively. You can directly enter your glucometer reading into this tool to immediately get the corresponding mmol/L value, making it easy to communicate with doctors, maintain a blood sugar diary, and compare with previous lab results. It's recommended to record values in both units in your blood sugar log for direct reference at your next doctor visit.
Why can't HbA1c (glycated hemoglobin) be converted with this tool?
HbA1c reflects average blood sugar levels over the past 2-3 months. It is not a blood sugar concentration itself. Units are NGSP percentage (%) or IFCC-recommended mmol/mol (millimoles per mole). The conversion formula is: IFCC(mmol/mol) = (NGSP(%) - 2.15) × 10.929. This is not a simple multiplication/division factor and is completely different from the linear mg/dL↔mmol/L conversion. A dedicated HbA1c conversion table or tool is required.
How many decimal places should conversion results show? Should I round?
In home glucometers and daily self-monitoring, mg/dL is typically an integer (e.g., 95, 128 mg/dL), while mmol/L typically shows one decimal place (e.g., 5.3, 7.1 mmol/L). This tool uses full floating-point calculation internally, displaying results to sufficient precision. Users may round as per their own habit when recording. For example, recording mmol/L to 1 decimal place and mg/dL as integers will not introduce clinically meaningful error.
Will my blood sugar values be uploaded? Is it private and secure?
Completely not uploaded. The entire conversion logic uses pure frontend JavaScript running in your local browser. No network requests are made with the values you enter - the server cannot see any of your blood sugar data. When you close the browser tab, input content is immediately cleared. No cookies or localStorage health records are kept. Suitable for privacy-sensitive scenarios: people with diabetes, healthcare professionals, pregnant women (gestational diabetes monitoring), and others can use with confidence.
Why are reference ranges slightly different for urine glucose, fingerstick blood, and venous blood?
The unit conversion factor is the same for any body fluid sample (since glucose molecular weight is fixed). The difference is in reference value ranges: venous plasma glucose (hospital lab) is approximately 10-15% higher than fingerstick whole blood glucose; diagnostic standards are based on venous plasma. Urine glucose is expressed semi-quantitatively as +/-/+++ or mg/dL; normal urine glucose should be negative (renal threshold approximately 10 mmol/L / 180 mg/dL). Regardless of sample type, the mg/dL↔mmol/L conversion factor of 18.016 applies.
Why do some sources say divide by 18, others by 18.016, others by 18.02?
This is a precision rounding difference. Precise calculation: 1 mmol/L = 180.156 mg/L = 18.0156 mg/dL ≈ 18.016 mg/dL; 1 mg/dL = 0.055508 mmol/L. Different organizations use slightly different values for glucose molar mass (180.1559, 180.16, 180.18, etc., historical versions), but the deviation between all versions is less than 0.04%, completely negligible for clinical use. WHO, ADA, IDF, and other authoritative organizations often simplify to 18 in educational materials for easy mental math.
Why can't I use a general unit app or calculator to convert blood sugar?
General unit calculators often treat mg/dL and mmol/L as generic concentration units (using water or some default substance factor). If the factor is wrong, incorrect results are produced; or they lack clinical reference range prompts for blood glucose. This tool is locked to glucose-specific factor with medical zone markers for low/normal/high blood sugar, preventing users from misusing general tools to get incorrect values that could affect health decisions.
Are pregnancy blood sugar standards the same as for the general population?
Gestational Diabetes Mellitus (GDM) diagnostic criteria are stricter than for general adults: fasting ≥5.1 mmol/L (92 mg/dL), 1-hour post-load ≥10.0 (180), 2-hour post-load ≥8.5 (153) is diagnostic (any one value triggers diagnosis). Control targets typically recommend fasting <5.3, 2-hour postprandial <6.7. The conversion factor remains 18.016; only reference ranges differ. This tool converts units correctly, but please strictly follow your obstetrician's guidance for diagnosis and glucose control targets.
