The Vitamin D Metabolite Ratio (VMR) measures the ratio of 24,25(OH)₂D₃ to 25(OH)D₃ in your blood, expressed as a percentage. While the standard 25(OH)D test tells you how much Vitamin D is circulating, the VMR reveals how well your body is metabolising and regulating it.
A healthy VMR (5.7–14.4%) indicates that your body’s Vitamin D metabolism pathway (CYP24A1 enzyme) is functioning correctly. A low VMR (<4.3%) may suggest impaired catabolism — meaning your body isn’t efficiently processing Vitamin D, which can indicate genetic variants affecting CYP24A1, kidney dysfunction, or other metabolic issues. This is particularly useful for patients who have persistently low Vitamin D levels despite adequate supplementation.
The Vitamin D test measures 25(OH)D (25-hydroxyvitamin D) in your blood, the most stable marker of your Vitamin D status. This reflects your Vitamin D intake from diet, supplementation, and sun exposure, and is the gold standard for assessing your nutritional Vitamin D levels.
Vitamin D is unique among vitamins because your body can synthesise it from sunlight exposure (UVB radiation converts cholesterol in the skin to Vitamin D3). However, many people are deficient due to limited sun exposure, geographic location, darker skin pigmentation, use of sunscreen, and seasonal variation. Dietary sources include oily fish, egg yolks, fortified foods, and supplements.
Once produced or ingested, Vitamin D is converted in the liver to 25(OH)D and then activated in the kidneys to its hormone form, 1,25(OH)₂D, which regulates calcium absorption, bone mineralisation, and immune cell function. Optimal levels (30–50 ng/mL) are associated with improved bone health, immune function, mood stability, and reduced risk of chronic diseases including cardiovascular conditions and autoimmune disorders.
| Species | Vitamin D (IU) | Vitamin D (µg) | Content | Notes |
|---|---|---|---|---|
| Cod Liver Oil (1 tbsp) | 1,360 | 34.0 | High | Richest natural source |
| Herring (Atlantic) | 1,628 | 40.7 | High | Fresh, pickled, or smoked |
| Rainbow Trout | 645 | 16.1 | High | Farmed or wild |
| Salmon (wild) | 600–1,000 | 15–25 | High | Wild higher than farmed |
| Swordfish | 566 | 14.2 | High | Excellent source |
| Mackerel | 360 | 9.0 | High | Also rich in Omega-3s |
| Sardines (canned) | 272 | 6.8 | High | Affordable, with bone for calcium |
| Tuna (canned) | 236 | 5.9 | Moderate | Light or white varieties |
| Mushrooms (UV-exposed) | 400–1,000 | 10–25 | High | Best plant-based source |
| Egg Yolks (2 large) | 80 | 2.0 | Low | Varies by feed & sun exposure |
| Supplement Type | Strength (IU) | Form | Notes |
|---|---|---|---|
| Vitamin D3 Tablets | 1,000 | D3 (cholecalciferol) | Recommended daily dose |
| Higher Strength D3 | 2,000–4,000 | D3 (cholecalciferol) | Only under HCP guidance |
| Liquid D3 Drops | 400–1,000/drop | D3 (cholecalciferol) | Easy dosing, suitable for children |
| D3 + K2 Combination | 1,000 | D3 + Vitamin K2 | K2 directs calcium to bones |
| D3 + Calcium | 400–1,000 | D3 + Calcium | Supports bone mineralisation |
| D3 Oral Spray | 1,000 | D3 (cholecalciferol) | Fast absorption via oral mucosa |