Pick up a vitamin D supplement and the label will usually say D2 or D3. Most of us never stop to ask whether that small number makes a difference. New research suggests it might matter more than we thought.
- Vitamin D comes in two main forms: D2 from plants and fungi, and D3 from sunlight and animal foods.
- A review of clinical trials found that people taking D2 had lower levels of D3 in their blood.
- D2 still raises total vitamin D, so it is not useless, but D3 appears to work better for most people.
- Early lab research hints that D3 may also play a stronger role in immune signalling, though this is not yet proven.
- A simple blood test is the best way to know your vitamin D status before choosing a dose.
So, is vitamin D3 better than D2? For most people, the answer appears to be yes. A systematic review published in Nutrition Reviews by researchers at the University of Surrey, the John Innes Centre and Quadram Institute Bioscience looked at randomised controlled trials and found that taking vitamin D2 was linked to a drop in the body's vitamin D3 levels. D2 still adds to your total vitamin D, but it seems to do so partly at the cost of D3. That is why the authors suggest D3 may be the more useful choice for most people, while noting that individual needs can differ.
What Is the Difference Between Vitamin D2 and D3?
Both forms belong to the same family of nutrients that help your body absorb calcium and keep bones and muscles working well. The difference lies in where they come from. Vitamin D2, also called ergocalciferol, is made by plants and fungi. Mushrooms exposed to sunlight or UV light are a common source, and D2 is often used in plant-based supplements and fortified foods.
Vitamin D3, or cholecalciferol, is the form your skin makes when it is exposed to direct sunlight. It is also found in egg yolks, oily fish such as salmon and sardines, and some fortified dairy. Once inside the body, both forms are converted in the liver to a compound called 25-hydroxyvitamin D, which is what doctors measure in a blood test.
What the New Review Found
The research team, led by Dr Emily Brown at the University of Surrey, screened 20 studies and pooled data from 11 of them for the main analysis. Compared with people who did not take D2, those who did had clearly lower levels of 25-hydroxyvitamin D3. The average drop was roughly 9 to 18 nmol/L, depending on how the numbers were analysed.
Why would this happen? Scientists do not have a firm answer yet. One idea is that when vitamin D levels rise, the body speeds up the breakdown and removal of vitamin D compounds. If that is true, adding D2 could cause some of your existing D3 to be cleared away faster. This is still a theory and needs more research.
This finding fits with earlier work. A previous set of 24 studies also found D3 was better than D2 at raising overall vitamin D status. You can read more about how vitamin D works and how much adults need on the NIH Office of Dietary Supplements vitamin D fact sheet.
Does D2 Still Have a Role?
Yes, and it is important not to overstate the findings. D2 does raise total vitamin D levels. A 2026 review of 26 randomised trials found that D2 lowered parathyroid hormone and caused a small rise in blood calcium, which shows it has real effects in the body. For strict vegans, D2 has long been the easy option, though vegan D3 made from lichen is now widely sold.
There is also an open question about health outcomes. Lower D3 levels on paper do not automatically mean worse bones or more illness. The researchers themselves say larger studies are needed to see whether this difference changes how people actually feel or how often they get sick.
A Possible Link With Immunity
A separate study from the same university, led by Professor Colin Smith and published in Frontiers in Immunology, looked at gene activity in blood. It found that D3, but not D2, seemed to switch on a type of immune signalling called type I interferon, which is part of the body's early defence against viruses. This is interesting, but it is based on gene activity, not on counting infections. It does not prove that D3 prevents illness.
What This Means for Your Daily Routine
For many people in India, low vitamin D is common despite plenty of sunshine, because of indoor lifestyles, covered clothing and pollution. If you are thinking about a supplement, a few simple steps can help:
- Get a 25-hydroxyvitamin D blood test before starting, so you know where you stand.
- If your doctor recommends a supplement, ask whether D3 is suitable for you.
- Take vitamin D with a meal that contains some healthy fat, since it is a fat-soluble vitamin. Our guide to food combinations that improve nutrient absorption explains why this matters.
- Do not stop eating food sources. Eggs, sun-dried mushrooms and fortified milk all add to your daily intake.
- Spend a short time in morning or midday sun when you can, with your arms and face uncovered.
The bottom line is simple. Both forms of vitamin D can help, but the evidence now leans towards D3 as the more reliable choice for most people. Speak with your doctor about the right form and dose for you, especially if you take other medicines or have a health condition.
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Frequently Asked Questions
1. Is vitamin D3 better than vitamin D2?
For most people, vitamin D3 appears to be the better choice. Several reviews of clinical trials have found that D3 raises overall vitamin D levels more effectively than D2. A 2025 review in Nutrition Reviews also found that taking D2 was linked to lower D3 levels in the blood. Personal needs can differ, so check with a doctor.
2. What foods contain vitamin D2 and D3?
Vitamin D2 comes mainly from plant sources and fungi, especially mushrooms exposed to sunlight or UV light. Vitamin D3 is found in animal foods such as egg yolks, oily fish like salmon and sardines, and some fortified milk. Your skin also makes vitamin D3 when it is exposed to direct sunlight.
3. Should vegetarians take vitamin D2 or D3?
Vegetarians who eat eggs or dairy can get some vitamin D3 from those foods. Strict vegans often rely on D2, but vegan D3 made from lichen is now widely available. Since research suggests D3 raises vitamin D levels more reliably, a lichen-based D3 may suit vegans who want to avoid animal sources.
4. How can I tell if my vitamin D levels are low?
A simple blood test called 25-hydroxyvitamin D, often written as 25(OH)D, measures your vitamin D status. Low levels may show up as tiredness, bone or muscle aches, or frequent illness, but many people have no clear symptoms. Testing is the only reliable way to know, and a doctor can guide your dose.
