Inside: Feeling tired, foggy, or low for no clear reason? This post unpacks how vitamin D deficiency shows up, how to test your levels, and the safest ways to restore balance naturally.
When I first found out I was vitamin D deficient, I was not completely surprised. The risk factors were all there. I live in a northern climate with cooler temperatures, I work indoors, I wear sunscreen, I live a dairy free lifestyle. I also had symptoms for vitamin d deficiency. I felt tired, irritable, had muscle aches and I felt foggy. To make it worse, many of the vitamin D supplements made me feel worse – until I finally learned that it was the form of vitamin D that I was taking (animal based D3 derived from sheep’s wool) that was the problem.
Once I changed to a vegan D3 (derived from lichen) and worked on consistency and maximizing absorption then my body responded. My energy began to improve. My mood lifted. The world became less heavy.
If you are feeling off – tired, unmotivated or as if your body is not working with you – then low vitamin D may be part of the picture. Let’s look at what it does for you, how to find out if you are low, and the best ways to test and support your levels safely.
What is Vitamin D and Why Does it Matter?
Vitamin D works more like a hormone than a vitamin. Your body produces it when sunlight strikes your skin, but it is also involved in almost everything else – your bones, your mood, your hormones, your immune system depend on it [1].
Think of vitamin D as a backstage helper maintaining harmony:
- Helps your gut absorb calcium and magnesium
- Keeps bones and teeth strong
- Supports mental health and brain function
- Reduces inflammation
- Affects how your body produces and uses hormones
When vitamin D drops too low, that balance starts to unravel.
Symptoms for Vitamin D Deficiency
The tricky thing about vitamin D deficiency is that it’s not always obvious. Symptoms creep in gradually, often overlapping with stress or burnout. Possible symptoms are:
- Low energy or fatigue no matter how much you sleep
- Brain fog or forgetfulness
- Mood dips, anxiety, or mild depression
- Muscle or joint pain
- Frequent colds or slow healing
- PMS changes or hormone imbalance
- Hair thinning or brittle nails
- Digestive problems, especially if you have gut inflammation
If several of these sound familiar, your body is asking for support [2].
What Causes Vitamin D Deficiency
Even people who eat well and spend time outdoors can suffer from it. It’s surprisingly common—especially in northern climates like in Canada. The reasons are:
- Limited sunlight: Long winters, cloudy days, or working indoors mean less UVB exposure.
- High sunscreen use: Protects skin (which is good!) but also blocks vitamin D production.
- Gut issues: Conditions like IBS, celiac, or low stomach acid affect absorption.
- Liver or kidney dysfunction: These organs activate vitamin D.
- Higher body fat: Vitamin D can get stored in fat tissue instead of circulating in your blood.
- Age and genetics: Older adults and some genetic variations affect conversion efficiency [3].
- Certain medications: Steroids, anticonvulsants, and weight-loss drugs can interfere.
Vitamin D2 and D3: What is the difference?
For supplemental vitamin D, you’ll see both D2 and D3 on labels. Here’s what they mean:
- Vitamin D2 (ergocalciferol): Made from plants or fungi. It helps, but doesn’t last as long in your body.
- Vitamin D3 (cholecalciferol): Usually animal-derived (lanolin). It’s stronger and stays in your system longer.
The research shows that D3 will elevate and hold blood levels more effectively than D2 [4]. If you’re vegan, or for those who are sensitive to lanolin-like properties (like myself), a D3 derived from lichen can be more well tolerated— it’s plant-derived but performs just like the traditional form.
How to Test Your Vitamin D Levels
1) Through Your Doctor.
The most accurate way is by a blood test known as the 25-hydroxy vitamin D [25(OH)D] blood test. This test is performed by a full blood draw (done in a lab) and gives the clearest picture of your status [5].
If you’ve been supplementing or suspect chronic low levels, this test is the gold standard.
2) At-Home Blood Spot Kits
If testing from home is more your style, there are several reputable dried blood spot kits where you mail in a tiny finger-prick sample to a certified lab. They are not as accurate, but generally helpful for tracking.
• For Canada: RxHomeTest
• For U.S.: Everlywell, CVS Health, or RxHomeTest
If your result comes back low, check with your doctor for confirmation through a complete blood draw.
What are Optimal Levels of Vitamin D?
Results are reported by labs in either ng/mL (U.S.) or nmol/L (Canada). Here’s the breakdown:
- Deficient: below 20 ng/mL (50 nmol/L)
- Insufficient: 20–30 ng/mL (50–75 nmol/L)
- Optimal range: roughly 30–100 ng/mL (75–250 nmol/L)
- Toxic: over 100–125 ng/mL (250–300 nmol/L) [6]
Many practitioners aim for a sweet spot of 40-60 ng/mL (100-150 nmol/L), but your best range depends on your health, genetics and lifestyle.
If you’re curious how vitamin D interacts with hormones or mood, check out my post on balancing hormones naturally — it dives deeper into how nutrients like vitamin D influence PMS, energy, and emotional balance.
Natural and supplemental sources of vitamin D can help improve energy and mood.
How to Support Healthy Vitamin D Levels
1. Get Safe Sun Exposure
A few minutes of sunlight on your face and arms (without sunscreen) two to three times per week will help boost production. Midday sun helps the most but apps, like dminder, are helpful for tracking your exposure and helping you avoid burning.
2. Eat Foods Rich in Vitamin D
Include salmon, sardines, tuna, egg yolks, mushrooms and fortified plant milks. You will not get enough vitamin D from food sources alone, but it helps.
3. Supplementing (Wisely)
For most adults taking 500-1,000 IU is usually well-tolerated and considered safe. If your levels are low, your doctor might suggest more — but don’t take large doses without checking with your doctor.
Taking too much vitamin D can cause calcium to build up in tissues, which can cause nausea, kidney problems, and irregular heart rhythms. In rare cases, chronic high doses can cause vitamin D toxicity, which is very serious [6].
High dose supplementation should only be continued under the supervision of a healthcare provider. I was able to raise my levels in weeks by consistently taking 1000IU daily and focusing on supporting my gut health. More is not necessarily better-no matter what social media says. Consistency and maximizing absorption is what is important.
4. Take With Fatty Foods and with Vitamin K2
Vitamin D is fat soluble, so take it with foods that contain healthy fats (avocado, nuts, olive oil, etc.). Also, taking it with vitamin K2 helps your body use calcium properly — directing it into bones instead of soft tissue.
5. Support Gut Health
If your digestion isn’t great, you are probably not absorbing vitamin D as well as you could. Gut inflammation, dysbiosis, and low stomach acid all play a role. Learn more about improving gut health in my post on stool testing kits and the best probiotics for gut health.
Your Next Steps
- Listen to your body. If fatigue, anxiety, or poor immunity are dragging you down, consider vitamin D as part of the puzzle.
- Test instead of guessing. Start with your doctor, or use a mail-in kit if that’s easier.
- Stay consistent. Once you start supplementing, retest after three months to see how your body’s responding.
- Keep it balanced. Pair your vitamin D with a nutrient-dense diet, good fats, and stress support.
Low energy, brain fog, or feeling run-down can be signs your iron needs support. This free guide and meal plan share simple, food-first ways to support iron absorption, steady your energy, and rebuild your iron levels naturally.
Final Thoughts
Paying attention to your symptoms for vitamin D deficiency, as well as risk factors is a great first step to restoring balance. This can help you decide if testing and supplementation is necessary. Vitamin D is not a magic pill, but it is one of those nutrients that can change everything when you finally get enough. The goal isn’t perfection — it’s balance.
Test, don’t guess. Supplement wisely. And most importantly, take care of the whole picture — your stress, your gut, your rest.
If you would like a free resource to get started, get my 5 Ways to Support Iron Levels Naturally — it’s packed with simple, science-backed tips to support iron levels, calm cravings, reset your gut, and steady your mood. Check out all the free guides in the freebies library.
And if you are ready to go deeper, join me in The Calm and Clear Method– a 3-month personalized journey to help restore your digestion, soothe anxiety, balance your nervous system and restore vibrant energy.
You deserve to feel strong, clear-headed, and balanced again- vitamin D is just one piece of the puzzle.
Be well,
Alysha Breanne
Thanksgiving Bonus Week Freebie: Vitamin D Deficiency Self-Check Guide
As a thank-you to my amazing readers this Thanksgiving, I’m sharing a special free resource — my Vitamin D Deficiency Self-Check Guide.
It’s a 2-page printable checklist to help you spot the signs of low vitamin D, understand your risk factors, and learn how to test and support your levels safely.
✨ No sign-up needed — it’s my way of saying thanks for being part of this growing wellness community.
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Alysha Breanne, CHN, CFNP — Certified Holistic and Functional Nutritionist helping women with iron deficiency, low ferritin, fatigue, and absorption issues restore steady energy using personalized nutrition and testing when needed.