Vitamin D: van Groningen model estimate

25(OH)D in two unit systems and a weight-based research estimate. No automatic treatment schedule.

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Result

Current 25(OH)D: 42.0 nmol/L
Total van Groningen estimate: 99000 IU

Van Groningen 2010 model. The result does not establish a need for treatment. Reference ranges are population benchmarks from the cited sources. Laboratories use their own ranges, and interpretation depends on clinical context: discuss the result with your physician.

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How it is calculated

The van Groningen (2010) model relates total cholecalciferol dose to weight and baseline 25(OH)D. This tool uses the fixed research target of 75 nmol/L, baseline below 50 nmol/L and weight 35–125 kg. The lower weight limit restricts this interface to an adult context; age and clinical exclusions require clinician assessment. It does not select a dosing schedule, maintenance dose or follow-up interval. Endocrine Society 2024 does not establish a universal target 25(OH)D for disease prevention in healthy people.

Formula

Total model estimate (IU) = 40 × (75 − 25(OH)D, nmol/L) × weight (kg). 1 ng/mL = 2.496 nmol/L.

Limits of the method

A research calculation for discussion with a clinician, not an individual prescription. Do not use it for self-treatment during pregnancy, in children, or with calcium disorders, kidney disease, malabsorption or granulomatous disease. The model does not account for medicines or supplements; the total must not be taken as a single dose.

Sources of the method

This calculation is for reference only and is not medical advice, a diagnosis or a prescription. If you have a medical condition, are pregnant, take medication or have any doubts, discuss the result with a physician or a qualified nutrition professional.

How to use the vitamin D model

Enter measured 25(OH)D

25-hydroxyvitamin D (calcidiol) specifically, not 1,25(OH)₂D. Report units are nmol/L or ng/mL; pick the right one and the calculator converts.

Check applicability

The 75 nmol/L target is fixed by the study, not selected as a universal normal value. This tool does not calculate the model at baseline levels of 50 nmol/L or above.

Enter body weight

Discuss the estimate with a clinician. The number does not determine a product, single dose or dosing frequency.

Vitamin D dose worked examples

Model example140,000 IU total

25(OH)D 25 nmol/L, target 75, weight 70 kg

40 × (75 − 25) × 70 = 140,000 IU. This is the arithmetic model result, not administration instructions.

Treatment scheduling is outside this calculation.

Different weight102,600 IU total

25(OH)D 48 nmol/L, weight 95 kg

40 × (75 − 48) × 95 = 102,600 IU. The model does not add an obesity-specific maintenance dose.

Do not interpret the total estimate as a single dose.

Model boundaryNot applicable

25(OH)D 80 nmol/L, target 75, 60 kg

Baseline 80 nmol/L is outside the deficient range used by this model. This does not determine whether supplements are needed.

No dose is shown outside model scope.

Why the formula includes weight

The authors described a relationship between change in 25(OH)D and dose per kilogram. There was substantial variability (R² = 0.38). The calculation does not guarantee an individual will reach the target.

Why no dosing schedule is provided

A research total does not establish safe dosing frequency or duration. Clinical context and other sources of vitamin D need separate assessment.

Model applicability boundaries

25(OH)D	Calculation context	Limitation
< 30 nmol/L (< 12 ng/mL)	In model scope below 50 nmol/L	Does not determine treatment
30–49 nmol/L (12–19 ng/mL)	In model scope below 50 nmol/L	Does not determine treatment
50–74 nmol/L (20–29 ng/mL)	Outside model scope	Does not determine treatment
75–125 nmol/L (30–50 ng/mL)	Outside model scope	Does not determine treatment
> 250 nmol/L (> 100 ng/mL)	Outside model scope	Does not determine treatment

This table describes the model, not universal treatment targets.

Frequently asked questions

How much vitamin D should an adult take?

This calculator cannot select a daily dose. It shows only a total research estimate to discuss with a clinician.

Can I take 10,000 IU a day?

The calculator does not establish the safety of that dose. High doses require an individual clinical decision considering contraindications and other medicines.

When should I retest?

The need and timing for repeat testing depend on indications and treatment. Routine 25(OH)D screening solely for disease prevention is not recommended in healthy people (Endocrine Society 2024).

D2 or D3?

The original model studied cholecalciferol D3. It does not convert D2 doses or select a product.

Do I need vitamin K2 with D3?

There is no convincing evidence that K2 is needed at standard D3 doses. It is discussed at high doses and with vascular calcification risk but is not routinely required. Adequate dietary calcium and magnesium matter more.

Why is the dose higher in obesity?

Weight is part of the research formula. This tool does not apply a separate obesity multiplier or calculate a maintenance dose.

Check other deficiencies and related markers:

Nutrient deficiency risk screening →Lab Unit Converter →Albumin-Corrected Calcium Calculator →Omega-3 Intake & Index Calculator (EPA + DHA) →

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What next

Formula breakdowns, biomarker reference ranges and nutrition articles with cited sources are in the NutriFit knowledge base.

Go to the knowledge base