Vitamin D, sometimes called the “sunshine vitamin,” helps keep your bones strong, your muscles working well, and your immune system healthy. But in winter, the sunlight in the UK isn’t strong enough for your skin to make enough vitamin D. Since most people also spend more time indoors during this season, it’s easy to become low in this important vitamin.
The good news is, you don’t have to depend on sunshine alone. By eating the right foods, taking supplements, and following a few simple habits, you can keep your vitamin D levels healthy all winter.
This guide will show you how to spot signs of low vitamin D, choose the best supplements for winter, and build a daily routine that helps you stay healthy, energetic, and positive even on the darkest days.
Why Vitamin D Drops in Winter
In winter, our bodies produce less vitamin D due to changes in sunlight, lifestyle, and weather. Understanding why this happens can help you find simple ways to keep your vitamin D levels healthy.
1. Weaker Sunlight
Your skin makes vitamin D when sunlight hits it, but it needs a special type of light called UVB. In winter, the sun is lower in the sky, and the light is weaker. This means your skin can’t make enough vitamin D, even if you go outside.
Studies show that in countries far from the equator, like the UK, UVB light is too weak in winter to produce much vitamin D at all. So, during this time, you need to get vitamin D from food or supplements instead.
2. Lower Vitamin D Levels in the Blood
Scientists have found that people’s vitamin D levels naturally fall during autumn and winter. In the UK, one study showed that average vitamin D levels dropped from around 51 nmol/L in September to about 38 nmol/L by March.
This means many people start winter with okay levels but end up low by the end of the season unless they take action.
3. Limited Vitamin D Storage
Some people believe the body stores enough vitamin D from summer to last all winter. However, research shows this isn’t always true.
While your body can keep some vitamin D in fat and muscle, it often isn’t enough to last through several months without sunlight. That’s why it’s important to keep topping up your vitamin D through your diet or supplements.
4. Indoor Life and Warm Clothing
Even when there is some sunshine, most of us spend more time indoors during winter. When we go out, we’re often wrapped up in coats, scarves, and hats, which cover most of our skin.
Cloudy weather and air pollution also block UVB light, and sunscreen can reduce vitamin D production, too. All these things make it harder for your body to make vitamin D naturally.
5. Delay Before Levels Drop
There’s usually a delay between when sunlight weakens and when vitamin D levels actually fall. This happens because vitamin D stays in your body for a few weeks before dropping in levels.
That’s why it’s smart to start eating vitamin D-rich foods or taking supplements early in the autumn, before your levels get too low.
In short, weaker sunlight, less outdoor time, warm clothing, and your body’s limited storage all play a part in winter vitamin D decline. Knowing this makes it easier to plan and keep your levels healthy throughout the colder months.
Vitamin D Deficiency Symptoms: What to Watch For
Vitamin D is important for strong bones, muscles, and your immune system. When your levels are low, it can affect how you feel and how your body works. The symptoms often come on slowly, so it can be easy to miss them. Here are some common signs to look out for.
1. Feeling Tired All the Time
Always feeling tired or low on energy can be an early sign of low vitamin D. Studies show that people with low vitamin D levels often feel more worn out, and their energy improves when their vitamin D returns to normal.
2. Weak Muscles and Body Aches
Vitamin D helps your muscles work properly. If you don’t get enough, your muscles might feel weak or sore, especially in your thighs, hips, or shoulders.
3. Bone or Joint Pain
Vitamin D helps your body absorb calcium, which keeps your bones strong. Low levels can cause bone or back pain and weaken your bones over time.
4. Getting Sick More Often
Vitamin D helps your immune system fight infections. When levels are low, you might catch a cold or the flu more easily, especially in the winter months.
5. Low Mood or the “Winter Blues”
Some people feel sad or depressed during darker months when there’s less sunlight. Low vitamin D can play a role in these mood changes because it affects brain chemicals like serotonin.
6. Slow Healing
If cuts or wounds take longer than usual to heal, it might be a sign that your body isn’t getting enough vitamin D, which helps with cell repair and growth.
When to Get Tested
Because these symptoms can have many causes, the best way to know if you’re low in vitamin D is to get a blood test. This test measures how much vitamin D is in your body.
If you often feel tired, achy, get sick easily, or notice mood changes in the winter, talk to a doctor about checking your vitamin D levels. Catching a deficiency early makes it easier to treat and can help you feel better faster.
|
Symptom |
What It Means |
Why It Happens |
|
Feeling Tired All the Time |
Ongoing fatigue or low energy |
Low vitamin D can reduce energy and cause tiredness |
|
Weak Muscles and Body Aches |
Muscle weakness or soreness (especially in thighs, hips, or shoulders) |
Muscles need vitamin D to work properly |
|
Bone or Joint Pain |
Aching bones or back pain |
Low vitamin D affects calcium absorption and bone strength |
|
Getting Sick More Often |
Frequent colds or flu |
Vitamin D supports your immune system |
|
Low Mood or “Winter Blues” |
Feeling sad or low during the darker months |
Vitamin D affects mood-regulating brain chemicals like serotonin |
|
Slow Healing |
Cuts or wounds take longer to heal |
Vitamin D helps with cell growth and repair |
Test First, Then Tweak: Understanding Your Vitamin D Levels
Before you change your diet or start taking supplements, it’s important to know your current vitamin D level. Everyone’s needs are different depending on age, skin tone, lifestyle, weight, and health. Testing helps you find out exactly where you stand so that you can avoid both too little and too much vitamin D.
1. What a Vitamin D Test Measures
A vitamin D test checks something called 25-hydroxyvitamin D [25(OH)D] in your blood. This shows how much vitamin D your body has stored and used from sunlight, food, and supplements.
It’s the most accurate way to find out your vitamin D status. Test results are usually shown in either nanomoles per litre (nmol/L) or nanograms per millilitre (ng/mL). To convert, multiply ng/mL by 2.5.
2. Understanding Your Results
Different organisations have slightly different guidelines, but these are general ranges used by health experts:
- Deficient: less than 30 nmol/L (or less than 12 ng/mL)
- Insufficient: 30-50 nmol/L (12-20 ng/mL)
- Sufficient: 50-125 nmol/L (20-50 ng/mL)
- High: over 125 nmol/L (50 ng/mL)
Your ideal level might vary based on your personal health, so it’s best to talk with a doctor or clinician before making any changes.
3. How to Get Tested
You can check your vitamin D levels in several ways:
- Through a blood test ordered by your GP or doctor
- Using a private health service that offers tests you can request yourself
- With an at-home finger-prick test, which uses a few drops of blood
Most home tests send your results online within a few days. They can be as accurate as lab tests if they’re done properly.
When choosing a home test kit, make sure it:
- Uses an accredited laboratory (for example, ISO 15189 certified)
- Clearly explains how your sample is tested (the LC-MS/MS method is the most reliable)
- Protects your privacy and data
4. When and How Often to Test
When you test, it can make a difference:
- Late autumn or early winter: Shows if you have enough vitamin D stored for the darker months
- Late winter or early spring: Shows if your levels dropped and whether supplements helped.
- After starting supplements: Retest after about 3-4 months to see if your levels improved.
Regular testing helps make sure your vitamin D stays in a healthy range all year.
5. Avoid Guesswork
You can’t always tell if you’re low in vitamin D just by how you feel. Some people have low levels without apparent symptoms, and others may have similar symptoms for different reasons.
Since vitamin D is fat-soluble, extra amounts can build up in your body if you take too much. Testing first helps you find the right balance safely and avoid taking more than you need.
Food First: Vitamin D-Rich Choices
Sunlight is the best natural source of vitamin D, but in winter, when days are shorter, food becomes very important. While not many foods naturally contain vitamin D, eating the right mix of natural and fortified options can help you stay healthy.
1. Natural Food Sources of Vitamin D
Only a few foods naturally have reasonable amounts of vitamin D. Most come from animals because vitamin D is stored in fat.
- Oily fish: Salmon, sardines, mackerel, herring, and trout are some of the best sources.
A 100 g serving of salmon can give you between 10 and 25 micrograms (400–1,000 IU) of vitamin D. Wild salmon usually has more vitamin D than farmed salmon. - Egg yolks: Hens that get sunlight or special feed lay eggs with more vitamin D. Each yolk can have about five micrograms (200 IU).
- Liver and cod liver oil: These are strong sources of vitamin D and also contain healthy fats like omega-3.
- Mushrooms exposed to UV light: When mushrooms are treated with UV light, they make vitamin D2. A 100 g serving can have around 10 micrograms (400 IU).
Vitamin D2 isn’t quite as potent as D3, but it still helps and is great for vegetarians.
2. Fortified Foods
Because few foods naturally contain vitamin D, many everyday items have it added in (this is called fortification). Fortified foods can help keep your levels healthy through the winter.
Common fortified foods include:
- Milk and plant-based drinks (such as soy, oat, or almond milk)
- Breakfast cereals and oats
- Margarine and certain spreads
- Yoghurts and cheese alternatives
Studies show that eating fortified foods can raise vitamin D levels by 15–30 nmol/L over a few months.
Tip: Check food labels for “vitamin D,” “D2,” or “D3,” and look at how much you get per serving.
3. Vegetarian and Vegan-Friendly Sources
If you don’t eat animal products, there are still good options for getting vitamin D.
- UV-treated mushrooms are the best natural plant source.
- Fortified plant milks, cereals, and spreads are key for vegan diets.
- Some vegan supplements use D3 made from lichen (a type of plant), which works just as well as animal-based D3
4. Smart Shopping Tips
When choosing foods for vitamin D:
- Look for at least 2.5–5 micrograms (100–200 IU) per serving.
- Pick fortified foods you already eat, like milk or cereal.
- Eat vitamin D foods with healthy fats (like olive oil, avocado, or nuts) to help your body absorb it better.
- Combine several small sources instead of relying on just one food.
Example One-Day Winter Menu for Vitamin D
|
Meal |
Example |
Vitamin D Contribution |
|
Breakfast |
Fortified oatmeal with plant milk, chia seeds, and a boiled egg |
~4 µg |
|
Lunch |
Grilled salmon with roasted vegetables and olive oil |
~10–20 µg |
|
Snack |
Fortified yoghurt or a handful of almonds |
~2 µg |
|
Dinner |
Mushroom and lentil stew with fortified bread |
~3 µg |
|
Daily Total |
|
~19–29 µg (760–1,160 IU) |
(Values are estimates and can vary by brand or portion size.)
Food alone might not always give you enough vitamin D in winter, but it’s a great start. If needed, your doctor may recommend supplements to keep your levels steady and safe all year round.
Vitamin D Supplements in Winter: Guidance and Safety
When sunlight and food are not enough, vitamin D supplements can help keep your levels healthy through the winter months. The key is to use them safely and wisely. Here’s what you need to know.
1. Why Supplements Are Often Needed in Winter
In winter, your skin makes little or no vitamin D because there’s less sunlight. Even eating a healthy diet usually doesn’t give you enough.
Research shows that most people get less than 20% of their vitamin D from food. Taking supplements is a safe and effective way to stay healthy when sunshine is limited.
Supplements help prevent low energy, weak muscles, and poor immunity caused by vitamin D deficiency.
2. Vitamin D2 vs. Vitamin D3: What’s the Difference?
There are two main types of vitamin D supplements: D2 and D3.
- Vitamin D2 (ergocalciferol): Comes from plants like mushrooms or yeast exposed to UV light.
- Vitamin D3 (cholecalciferol): Usually made from animal sources such as lanolin (from sheep’s wool), but vegan D3 made from lichen is also available.
Studies show that D3 raises vitamin D levels more effectively than D2, but both work and can be helpful. If you’re vegan, D2 or plant-based D3 are good options.
3. How Much Vitamin D Do You Need?
The right amount of vitamin D depends on your age, weight, lifestyle, and health.
Here are general daily recommendations:
- Adults (19-70 years): 10-20 micrograms (400-800 IU) per day
- Older adults (70+ years): up to 25 micrograms (1,000 IU) per day
- People with darker skin or limited sun exposure may need slightly more, but only under medical advice
If a test shows you’re deficient, your doctor may recommend a higher dose for a short time. Necessary: Don’t increase your dosage without testing first. Too much vitamin D can be harmful.
4. Safety and Avoiding Too Much Vitamin D
Vitamin D is stored in body fat, so taking too much can cause it to build up. This can lead to nausea, weakness, or high calcium levels.
While vitamin D toxicity is rare, it usually happens from very high doses taken for months.
Experts say adults should not take more than 100 micrograms (4,000 IU) a day unless told to by a doctor.
Safety checklist:
- Don’t take megadoses unless prescribed.
- Count vitamin D from all sources, including multivitamins.
- If you take supplements regularly, get your blood levels checked every 3-6 months.
5. Choosing the Right Supplement
When buying vitamin D, check the label for:
- Vitamin D3 or vegan D3 (from lichen)
- Third-party testing or certification (for example, ISO, GMP, or NSF)
- Oil-based capsules or sprays for better absorption
- Simple ingredients without added fillers
Softgels, sprays, or liquid drops are often easiest to take and absorb well.
6. Pairing Vitamin D with Other Nutrients
Vitamin D works best with a few key nutrients:
- Vitamin K2: Helps move calcium into bones and teeth instead of blood vessels.
- Magnesium: Helps your body use vitamin D properly.
- Omega-3 fatty acids: Support bone and immune health.
Eating a balanced diet that includes these nutrients helps your supplement work better.
7. When to Take Your Supplement
Vitamin D is absorbed best with food that contains healthy fats, such as olive oil, nuts, or avocado.
It’s best to take it with your largest meal of the day, like breakfast or lunch. Taking it at the same time every day helps keep your levels steady throughout winter.
Testing your levels first, taking the right type and dose, and using your supplement safely with food are the best ways to keep your vitamin D balanced and your body healthy all winter long.
Conclusion: Take Charge of Your Vitamin D This Winter
Keeping your vitamin D levels healthy in winter is possible, even without sunlight. Eating the right foods, adding a good supplement, and building simple daily habits can make a big difference in how you feel. You can have more energy, stronger bones, and better immunity all season long.
If you are not sure about your vitamin D levels or need help choosing the right supplement, it’s best to talk with a doctor.
Mobi Doctor can help you do this from home. You can book an online consultation and speak with a trusted doctor about your symptoms, test results, and the best ways to stay healthy during winter.
