# Blood Sugar mmol/L vs mg/dL: Units Compared

> The United States reports blood glucose in mg/dL. Most other countries use mmol/L. Multiply mmol/L by 18.0182 to get mg/dL, or divide mg/dL by 18.0182 for mmol/L.

**Last updated:** September 2026
**URL:** https://bodyhealthcalculator.com/compare/blood-sugar-mmol-vs-mgdl

## Summary

Blood glucose is the same molecule whether your lab reports it in mg/dL or mmol/L. The difference is unit convention, not biology. The United States, Japan, and several other countries use milligrams per deciliter. Canada, the United Kingdom, Australia, and most of Europe use millimoles per liter.

Misreading units causes dangerous confusion. A fasting value of 6.1 mmol/L is normal prediabetes range, but 6.1 mg/dL would be fatal hypoglycemia. Always confirm the unit before interpreting a number or setting pump alarms.

*Blood sugar mmol/L vs mg/dL*

|  | mg/dL (US) | mmol/L (international) |
| --- | --- | --- |
| Conversion | mg/dL = mmol/L × 18.0182 | mmol/L = mg/dL ÷ 18.0182 |
| Normal fasting | 70 to 99 | 3.9 to 5.5 |
| Prediabetes fasting (ADA) | 100 to 125 | 5.6 to 6.9 |
| Diabetes fasting (ADA) | ≥126 | ≥7.0 |
| Typical post-meal target (diabetes) | <180 | <10.0 |
| Severe hypoglycemia | <54 | <3.0 |

Sources: [1] [2]

## When to use mg/dL

Use mg/dL when reading US lab reports, American diabetes education materials, most US glucometer displays, and ADA guideline tables. Fasting targets, A1c-linked estimated average glucose, and insulin dosing algorithms in US clinics assume mg/dL.

If you use a continuous glucose monitor sold in the United States, default units are almost always mg/dL. Pump therapy settings for correction factors and target ranges are configured in mg/dL unless you manually switch.

Research papers from American journals often report mg/dL even when authors work internationally. Checking the methods section prevents unit errors when comparing your home readings to study thresholds.

Sources: [1] [3]

## When to use mmol/L

Use mmol/L when reading labs from Canadian, European, or Australian health systems, WHO documents, and international clinical trials. mmol/L aligns with SI units used for other blood analytes like cholesterol and urea.

Travelers and immigrants often encounter both systems. A British patient moving to the US may need to relearn that their old fasting target of 5.5 mmol/L equals about 99 mg/dL, not 55.

Some scientific calculators and A1c-to-glucose conversions output both units. The ADAG study relationship (eAG in mg/dL ≈ 28.7 × A1c − 46.7) converts cleanly to mmol/L by dividing by 18.0182.

Medical devices sold in Europe often ship with mmol/L defaults. Before using a imported meter in the US, check whether the display can switch units or whether the strips and control solution match local labeling requirements.

Sources: [2] [4]

## How to convert between units

The molecular weight of glucose (180.16 g/mol) defines the conversion. Multiply mmol/L by 18.0182 to get mg/dL. Divide mg/dL by 18.0182 for mmol/L. Many apps round to 18 for mental math; clinical work should use the full factor.

Example: 140 mg/dL ÷ 18.0182 = 7.8 mmol/L. Example: 5.0 mmol/L × 18.0182 = 90 mg/dL.

HbA1c is reported as a percentage of glycated hemoglobin and does not convert with the same factor. Use dedicated A1c-to-average-glucose equations when linking A1c to daily glucose units.

When teaching unit conversion to patients, write both numbers side by side on a reference card. Example: 100 mg/dL = 5.6 mmol/L, 126 mg/dL = 7.0 mmol/L. Pattern recognition reduces arithmetic errors during sick days or travel.

Sources: [4] [5]

## Clinical thresholds in both units

The ADA defines diabetes diagnosis at fasting glucose ≥126 mg/dL (≥7.0 mmol/L) or A1c ≥6.5 percent. Prediabetes spans 100 to 125 mg/dL (5.6 to 6.9 mmol/L). These cutoffs are equivalent; only the label on the number changes.

Hypoglycemia tiers used in CGM alerts: Level 1 below 70 mg/dL (3.9 mmol/L), Level 2 below 54 mg/dL (3.0 mmol/L). Level 2 requires immediate treatment with fast-acting carbohydrate.

Pregnancy uses stricter targets. Gestational diabetes screening thresholds differ from non-pregnant adult cutoffs and should be interpreted only with obstetric guidance.

Sources: [1] [2]

## Limitations

Unit conversion does not fix meter accuracy problems, strip expiration, or hematocrit interference. Validate unusual readings with a laboratory plasma glucose when possible.

Whole blood fingerstick meters read roughly 10 to 15 percent lower than plasma-equivalent lab values on some devices. Know whether your meter reports whole blood or plasma-calibrated results.

This comparison supports education. Treatment decisions require a clinician who knows your medication regimen, symptoms, and full lab panel.

Online forums and social media posts often omit units entirely. If a glucose value looks implausible, verify the unit before commenting on whether it is high or low.

Sources: [3] [5]

## References

1. ADA. [Classification and Diagnosis of Diabetes](https://diabetes.org/about-diabetes/diagnosis)
2. ADA. [Standards of Care in Diabetes](https://diabetes.org/standards-of-care)
3. CDC. [National Diabetes Prevention Program](https://www.cdc.gov/diabetes/prevention/index.html)
4. Nathan et al. (ADAG). [Translating A1c into estimated average glucose](https://pubmed.ncbi.nlm.nih.gov/18540046/)
5. Kirk et al.. [Glucose monitoring and insulin delivery](https://pubmed.ncbi.nlm.nih.gov/20587715/)

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