5 Symptoms of Vitamin D Deficiency You Might Be Ignoring This Summer

It is the ultimate summer paradox. The sun is blazing, the days are long, and you are spending more time outdoors than you have all year. Logically, your Vitamin D levels should be at their peak. Yet, millions of Americans are walking around in the middle of July with critically low levels of the “Sunshine Vitamin.”

How is this possible? And more importantly, are you one of them?

As a Senior Health Editor, I often see a spike in readers searching for remedies for fatigue and mood slumps during the winter months. We call it the “Winter Blues.” But there is a silent epidemic occurring right now, under the bright summer sun. We assume we are covered, so we ignore the warning signs our bodies are desperately sending us.

From aggressive sunscreen use (which is necessary, but blocks Vitamin D production) to the reality of working 9-to-5 indoors while the sun shines outside, summer deficiency is real. Here are the 5 symptoms of Vitamin D deficiency you are likely ignoring or misattributing to the summer heat.

1. The “Heat Exhaustion” Trap: Unexplained Fatigue

The Common Assumption: “It’s just the heat. The humidity is draining my energy.”

The Reality: While high temperatures can certainly make you lethargic, Vitamin D deficiency manifests as a deep, bone-weary fatigue that hydration and air conditioning simply don’t fix.

Vitamin D is essential for mitochondrial function—the power plants within your cells. When your levels dip, your body struggles to generate energy efficiently. Several studies have linked low Vitamin D levels to self-reported fatigue. If you are sleeping seven to eight hours a night, staying hydrated, and still feel like you are dragging your body through mud, it might not be the heat index. It might be your blood work.

What to look for:
* Difficulty waking up in the morning despite a full night’s sleep.
* An energy “crash” in the mid-afternoon that caffeine doesn’t help.
* General physical heaviness.

2. The “Summer Blues”: Mood Shifts and Anxiety

The Common Assumption: “I’m just stressed about planning vacation,” or “I’m anxious about how I look in a swimsuit.”

The Reality: We associate Seasonal Affective Disorder (SAD) with winter, but low Vitamin D affects serotonin production year-round.

Vitamin D receptors appear in many areas of the brain, including those linked to depression. Research suggests that Vitamin D plays a crucial role in regulating mood and warding off depression. When levels drop, serotonin levels can plummet, leading to feelings of sadness, hopelessness, or heightened anxiety.

If you find yourself feeling unexpectedly down while everyone else is enjoying beach days and BBQs, do not brush it off as simple stress. Your brain might be starving for a critical nutrient.

3. The “Gardening Ache”: Bone and Lower Back Pain

The Common Assumption: “I overdid it playing volleyball,” or “My back hurts from weeding the garden.”

The Reality: This is one of the most dangerous symptoms to ignore. Vitamin D is the key that unlocks calcium absorption. Without enough D, your body cannot absorb the calcium you eat, so it begins to “steal” calcium from your bones to maintain blood levels.

This results in osteomalacia (softening of the bones). In adults, this often presents as a throbbing ache in the bones, particularly in the lower back, pelvis, hips, and legs. Unlike muscle soreness, which usually resolves after a few days of rest, bone pain from deficiency is persistent and often worsens at night.

Key differentiator: Press on your breastbone or shin bone. If it feels tender or painful to moderate pressure, this is a classic sign of Vitamin D deficiency, not just muscle overuse.

4. The “Chlorine Effect”: Excessive Hair Shedding

The Common Assumption: “The pool chlorine and ocean salt are drying out my hair and making it break.”

The Reality: While environmental factors can damage hair *quality*, nutritional deficiencies cause hair *loss*.

Vitamin D stimulates hair follicles to grow. When the body is low on this nutrient, it deprioritizes non-essential functions—and keeping a thick head of hair is considered non-essential compared to keeping your heart beating. Severe deficiency is strongly linked to alopecia areata, an autoimmune condition that causes patchy hair loss, but even moderate deficiency can trigger telogen effluvium (excessive shedding).

If you are noticing significantly more hair in your drain or brush this summer, don’t just buy a deep conditioner. Check your nutrient levels.

5. The “Summer Cold”: Slow Wound Healing and Frequent Illness

The Common Assumption: “I must have caught a bug from traveling,” or “This bug bite is just taking a while to heal because I keep scratching it.”

The Reality: Vitamin D is a master regulator of your immune system. It interacts directly with the cells that fight infection.

If you seem to catch every cold going around the office, or if minor cuts, scrapes, and bug bites take weeks to heal instead of days, your immune system may be compromised. The role of Vitamin D in controlling inflammation and infection is well-documented. In a season where we are active and prone to scrapes, slow healing is a red flag you shouldn’t ignore.

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Why Does This Happen in Summer?

You might be reading this and thinking, *”But I go to the beach every weekend!”* Here is why you might still be deficient:

1. Sunscreen: SPF 30 blocks about 97% of UVB rays. While this is vital for preventing skin cancer and aging, it also blocks the specific rays needed to synthesize Vitamin D.
2. Skin Tone: Melanin acts as a natural sunscreen. If you have darker skin, you need significantly more sun exposure than someone with pale skin to produce the same amount of Vitamin D.
3. The Angle of the Sun: Even in summer, if you are outside only in the early morning or late evening, the sun’s angle may be too low for UVB rays to penetrate the atmosphere effectively.
4. Showers: Some dermatological theories suggest that scrubbing your skin with soap immediately after sun exposure might interfere with the absorption of Vitamin D, which is synthesized in the oils on the skin’s surface (though this is debated, it is worth noting).
5. Obesity: Vitamin D is fat-soluble. If you have a higher body mass index (BMI), the vitamin can get “sequestered” in fat cells, preventing it from circulating in the blood where your body needs it.

How to Fix It (Safely)

Before you ditch the sunscreen and bake in the sun (which increases skin cancer risk), take a strategic approach:

* Get Tested:** This is the only way to know for sure. Ask your doctor for a **25-hydroxy vitamin D blood test. A level between 20 ng/mL and 50 ng/mL is considered adequate, though many functional medicine experts prefer levels closer to 50-70 ng/mL.
* Dietary Sources: Eat your way to better levels. Fatty fish (salmon, tuna, mackerel), egg yolks, and fortified foods (milk, orange juice, cereals) are excellent sources.
* Supplementation: This is often the most effective route. Vitamin D3 (cholecalciferol) is generally recommended over D2 for better absorption. Since it is fat-soluble, always take your supplement with a meal containing fat (like avocado or nut butter) to increase absorption by up to 50%.
* Smart Sun Exposure: Some experts suggest 10–15 minutes of midday sun exposure on the arms and legs *without* sunscreen, two to three times a week, before applying your SPF. However, always consult your dermatologist first, especially if you have a history of skin cancer.

The Takeaway

Don’t let the summer sun fool you. If you are feeling off-balance, tired, or achy, listen to your body. Vitamin D deficiency is common, easily testable, and highly treatable. Reclaiming your energy might be as simple as adding a supplement to your morning routine, allowing you to actually enjoy the rest of the season.

*Disclaimer: This content is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new supplement regimen.*