If I could only give my family one supplement…
Every fall, I get the same question: “If I could only take one thing for my immune system, what should it be?”
My answer is always the same: Vitamin D.
Why? Because it’s simple, affordable, safe and your body can’t run its defenses without it.
Yet most people (including kids!) are running low on Vitamin D by October, which is why colds, flu, and exhaustion hit so hard this time of year.
Why Vitamin D Matters: The Immune Spark Plug
Think of your immune system as an engine. Vitamin D is the spark plug that makes it start.
One of its most important jobs is to “wake up” your T-cells, the special forces of your immune system. T-cells identify intruders like viruses and bacteria, then direct the attack.
But here’s the catch: without Vitamin D, your T-cells stay asleep.
Low Vitamin D = a sluggish immune army that can’t fight back.
How to Check Your Vitamin D Levels
The best way to know your Vitamin D status is a 25(OH)D blood test (25-hydroxy vitamin D).
Ask your doctor for this test by name.
If you can’t get it through your doctor, look into private lab options.
Reach out if you need guidance I help clients navigate this all the time.
The Sweet Spot for Vitamin D
Deficiency: under 50 nmol/L (20 ng/mL).
Optimal for immune health: 75–125 nmol/L (30–50 ng/mL).
Caution: over 200 nmol/L (80 ng/mL) can be too high.
Aim for the sweet spot not too low, not too high.
When & How to Take Vitamin D
Take Vitamin D with a meal that has some healthy fat → it’s fat-soluble, so absorption improves.
Morning or lunchtime often works best (consistent daily use matters more than exact timing).
Pair Vitamin D with Vitamin K2 and Magnesium → this combo keeps bones strong, supports the heart, and makes sure calcium goes where it belongs (into your bones, not your arteries).
If you want recommendations on what types I recommend, see below!
The Best Vitamin D Options This Winter
When it comes to supplements, not all Vitamin D products are created equal. Some aren’t tested for purity or potency meaning you can’t be sure you’re getting what the label says.
That’s why I only recommend trusted professional-grade brands for my clients and family.
Here are my top 3 Vitamin D picks this winter:
1. Metagenics D3 Liquid (My Top Recommendation)
Why I love it: Easiest and most cost-effective way to take Vitamin D.
How much you get: Each bottle contains over 2,000 drops, perfect for families since you can adjust the dose for adults and kids.
Cost per drop: A fraction of a cent one of the best long-term investments for your health.
Purity + Potency: Every batch is tested for quality, so you know exactly what you’re getting.
Ease of use: Just one quick drop under the tongue or into a drink.
2. Vitamin D + K2 Combination (Designs for Health)
Why I love it: Combines Vitamin D with Vitamin K2 in one dropper, so you never forget to pair them.
Benefit: K2 directs calcium into your bones where it belongs, protecting your arteries and heart.
Best for: People who want an all-in-one solution with no extra steps.
3. Vitamin K2 Add-On
Already taking plain Vitamin D? Pair it with K2 for full benefits.
Check out this trusted Vitamin K2 option on Amazon.
This ensures you’re covering all your bases, especially for bone and heart health.
If you’re unsure which option is best for your family, start with the Metagenics drops for simplicity, and add K2 from Amazon if you’re not using a combo product.
What Happens When Vitamin D is Too Low
When your levels drop, you’re not just more prone to colds and flu. Low Vitamin D is linked with:
Weak immune response → frequent infections.
Fatigue, low energy, and “winter blues.”
Seasonal depression (SAD).
Weaker bones, aches, and muscle pain.
Higher inflammation throughout the body.
The Top 5 Ways Vitamin D Helps You This Winter
Stronger Immunity → T-cells wake up and fight viruses quickly.
Better Blood Sugar Balance → supports the pancreas and beta cells, improving insulin sensitivity.
Stable Mood & Energy → protects against the winter blues and fatigue.
Healthier Bones & Muscles → works with calcium + K2 for strength.
Lower Inflammation → keeps your body calm instead of stuck in “attack mode.”
Why Kids Need Vitamin D Too
Kids burn through nutrients as they grow, and Vitamin D is no exception. When kids are deficient, they:
Get sick more often (more colds, ear infections, respiratory bugs).
Miss more school days.
Struggle with mood and focus.
The fix is simple: Vitamin D drops. Just a few drops daily can strengthen their immune system and support healthy growth.
Quick Action Steps for Families
Ask for a 25(OH)D blood test (Vitamin D level).
Supplement daily in fall/winter (with K2 + Magnesium).
Eat Vitamin D-rich foods: salmon, eggs, mushrooms.
Make Vitamin D part of your Winter Immunity Toolkit.
Don’t wait until your family is already sick. Vitamin D is one of the simplest, most powerful ways to stay strong this winter and it’s something you can start today.
Download my free Winter Immunity Checklist for a step-by-step guide.
Or grab the Immune Support Bundle I use with clients, which starts with high-quality Vitamin D.
