Sweater Weather Ready? Don’t Skip Vitamin D3 with K2
When October rolls around, most people welcome the break from the heat. The air turns crisp, afternoons get shorter, and weekends fill with football games, warm drinks, and cozy sweaters. But as the sunlight fades, so does something your body relies on: vitamin D3.
Even before winter officially arrives, the cooler weather and longer nights start affecting your ability to produce vitamin D naturally. You may not notice the shift right away, but by late fall, your levels can drop enough to affect your energy, mood, and immune balance.
If you often feel more tired or under the weather more easily when the weather turns cool, a lack of vitamin D3 may be one reason why. Understanding how your body uses vitamin D3 in winter and how to support it through diet and supplementation can help you stay strong, focused, and steady through the darker months.
That’s where pairing vitamin D3 with K2 makes all the difference. This powerful combination supports calcium balance, supports bone health, and promotes a calm, resilient immune system, even when the days get shorter and the sunlight is weak.
Why Sunshine Alone Isn’t Enough
When the days get shorter, your skin doesn’t receive the same UVB light it needs to make vitamin D3 naturally. By November, even an hour outdoors may not provide much benefit, especially if you’re bundled up, using sunscreen, or heading to work before sunrise and coming home after dark.
You might think, “But I live in a sunny place, does that count?”
Not quite. Here’s why even southern states struggle to get enough D3 from sunshine alone:
1. The Sun’s Angle Changes
In summer, the sun’s rays hit your skin directly, which helps your body make plenty of vitamin D. By late fall, the sun sits lower in the sky, and those UVB rays lose their power long before they reach you.
2. Cooler Weather = Covered Skin
As the temperature drops, most of us swap T-shirts for sweaters and jackets. Even light layers like long sleeves and pants block nearly all UVB rays, cutting your vitamin D production to almost zero.
3. Indoor Living
Between work, errands, and screen time, most people spend about 90% of their day indoors. And here is the kicker, sunlight through windows does not help. Glass filters out UVB rays completely.
4. Stored D3 Runs Out
Your body does store vitamin D from the sunnier months, but those reserves do not last long. By November or December, your “summer savings” are usually gone unless you are getting enough through food or supplements.
Why Vitamin D3 with K2 Is the Smarter Combination
Vitamin D3 is essential for absorbing calcium, the mineral that keeps your bones and teeth strong. But calcium is like a resource that needs direction. Without the right partner, it can end up in the wrong places, like soft tissues or arteries, instead of in your bones where it belongs.
That is where vitamin K2 steps in. K2 acts like a traffic director, guiding calcium to your bones and teeth while helping keep your arteries clear and flexible.
When you take vitamin D3 and K2 together, they create the perfect balance:
- D3 boosts calcium absorption.
- K2 makes sure calcium goes exactly where it is needed.
- Together, they support bone health, support cardiovascular health, and help keep your immune system balanced all year long.
How Vitamin D3 with K2 Work Together Inside Your Body
Your body has an amazing process for using vitamin D3, but it depends on teamwork between several organs and between D3 and K2 themselves. Here is what happens behind the scenes.
- Sunlight or Supplements Start the Process
Your skin makes vitamin D3 when UVB light hits it, or you can take it as a supplement when sunlight is limited.
- The Liver Stores It for Later
Your liver turns that D3 into a stored form called 25-hydroxyvitamin D, the version your provider checks in a blood test.
- The Kidneys Activate It
Your kidneys then convert that stored D3 into calcitriol, the active form that tells your cells how to use calcium and helps regulate your immune system.
- Vitamin K2 Finishes the Job
K2 activates specific proteins that move calcium into your bones and teeth instead of leaving it in your arteries or soft tissues.
Together, vitamin D3 and K2 make sure calcium is absorbed, activated, and delivered to the right places. D3 sets the stage, and K2 ensures balance and safety.
The Latitude Effect: How Where You Live Affects Vitamin D3
Even in the U.S., sunlight strength varies dramatically depending on how far north you are. The farther you live from the equator, the longer your “vitamin D winter” lasts.
| City | Latitude | Months with Little to No Vitamin D Production |
| Houston, TX | 29.8°N | December–January (2 months) |
| Dallas, TX | 32.8°N | November–February (3–4 months) |
| Kansas City, MO | 39°N | October–March (5 months) |
| Chicago, IL | 41.9°N | September–April (6+ months) |
| Boston, MA | 42.4°N | September–April (6+ months) |
Even if you live in Houston or another southern city, the combination of shorter days, indoor work, and cooler air means your vitamin D levels are likely to drop through the fall and winter months.
Why Supplementation Matters
Even with a healthy diet and some sun exposure, most people cannot maintain optimal vitamin D levels in the fall and winter. Here is what helps the most.
1. Choose Vitamin D3 with K2
Look for a supplement that combines both nutrients. This pairing supports calcium balance, strong bones, and a healthy heart.
2. Add Magnesium and Omega-3s
Magnesium helps your body activate D3 efficiently, while omega-3s enhance absorption and support overall wellness.
3. Take It with Food
Since both D3 and K2 are fat-soluble, they absorb best when taken with meals that include healthy fats such as avocado, olive oil, or nuts.
4. Stay Consistent
Taking vitamin D3 with K2 regularly is key. Most people need more than they realize, especially during the cooler months when sun exposure is limited. Your ideal amount depends on your current levels, diet, and overall health. For personalized recommendations, call and speak with one of our Certified Nutritionists at 281-646-1659. Consistent supplementation helps maintain steady levels and lasting results.
Seasonal Support from Physicians Preference Vitamins
We make it easy to stay balanced through the cooler months with carefully formulated supplements designed to work together.
- Vitamin D3 + K2: The foundational pair for bone and heart health.
- Magnesium Glycinate: Supports relaxation and activates D3 for better use in the body.
- Omega-3 Fish Oil: Improves absorption of fat-soluble nutrients and supports brain and cardiovascular health.
Each one is designed to help you feel strong, energized, and supported when sunlight is in short supply.
Final Thoughts
As the days get shorter and the sunlight fades, your body naturally produces less vitamin D3. Even in warm or sunny states, most people cannot make enough to stay in the optimal range during fall and winter.
Taking vitamin D3 with K2 fills that seasonal gap. It supports your bones, your mood, your immune system, and your overall vitality, so you can stay well, active, and balanced even when the sun is not shining.
If you would like help choosing the right supplement plan for your needs, our Certified Nutritionists are here to guide you. Call 281-646-1659 or visit PhysiciansPreferenceVitamins.com to learn more.
These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.
