Low Vitamin D Symptoms: How They Affect Your Energy, Mood and Immunity

If you’ve been feeling tired, flat or catching every bug going, you’re not imagining it. Low vitamin D symptoms can creep in quietly and affect your energy, mood and immunity long before you realise what’s happening.

Vitamin D isn’t just about strong bones. It plays a role in hormone balance, gut health, muscle function, mood regulation and how well your immune system responds. And if you work indoors, live in the UK or haven’t seen the sun since that one warm week in April… your levels might not be where you think they are. Let’s break it down in a simple, no-nonsense way.

What Are the Signs of Low Vitamin D?

Low vitamin D symptoms can show up differently for everyone, but the most common signs include:

1. Low energy and constant fatigue

You might feel like you’re running on 20% battery even after a decent night’s sleep. Vitamin D plays a role in energy production, so when levels dip, your get-up-and-go can vanish.

2. Low mood or feeling “not yourself”

Vitamin D supports serotonin, your feel-good hormone. When your levels drop, you might notice mood dips, irritability or feeling less resilient.

3. Weakened immunity

If it feels like every cold, cough or bug finds you, this could be a sign. Vitamin D is crucial for immune balance and helping your body respond appropriately.

4. Muscle aches or general soreness

Low vitamin D can affect muscle function and recovery. Some people notice a dull ache, stiffness or feeling older than their age.

5. Gut issues

This might surprise you, but low vitamin D levels often show up in people with bloating, IBS symptoms or poor digestion. There’s a big gut-immune connection here, and vitamin D plays a role in that communication between systems.

Why So Many People Have Low Vitamin D

In the UK, it’s incredibly common, especially from October to April. We simply don’t get enough sunlight to make what we need.

Other reasons include:

• Working indoors

• Sunscreen use (important, but it blocks vitamin D production)

• Darker skin tones

• Digestive issues or poor absorption

• Perimenopause or hormonal shifts

• Chronic stress (which changes how your immune system behaves)

If you tick more than one of these, your levels could be on the low side without you knowing.

How Low Vitamin D Impacts Energy, Mood and Immunity

Here’s where it gets really interesting:

Energy

Vitamin D helps your mitochondria, your cells’ little energy factories, work properly. When levels dip, everything feels harder.

Mood

It helps regulate neurotransmitters, including serotonin. This is why mood changes are one of the most common early low vitamin D symptoms.

Immunity

Vitamin D acts like the immune system’s project manager. It helps your body respond effectively but calmly, reducing the likelihood of constant infections or inflammatory flare-ups.

So if you’ve been feeling flat, emotional or under the weather? It might not just be “one of those months.”

Should You Test Your Vitamin D Levels?

Short answer: yes, especially if you recognise any of the low vitamin D symptoms above.

A simple finger-prick test can give you a clear picture. I often run this with clients because symptoms alone never tell the full story. Testing means you get personalised guidance, not guesswork.

Practical Ways to Support Your Vitamin D Levels

1. Safe sunlight exposure

Just 15–20 minutes on arms and face in the warmer months can make a big difference.

2. Include vitamin D-rich foods

Think oily fish, eggs, mushrooms, fortified milks and yoghurts. Diet alone often isn’t enough, but it helps.

3. Supplement (but not blindly)

This is where personalised support matters. Too much vitamin D can cause issues just as too little can. I help clients find the right dose based on symptoms, lifestyle and test results.

4. Support your gut

A healthy gut helps you absorb nutrients properly, including vitamin D. Bloating, constipation, reflux or IBS may mean absorption isn’t where it should be.

Vitamin D Recipe: Creamy Lemon & Dill Salmon with Garlic Mushrooms

(A quick, simple dinner packed with natural vitamin D)

Serves: 2

Time: 20 minutes

Ingredients:

• 2 salmon fillets (rich in vitamin D3)

• 1 tsp olive oil

• 200g mushrooms, sliced (expose to sunlight beforehand if possible)

• 1 small garlic clove, minced

• Juice of ½ lemon

• 1 tbsp fresh dill (or 1 tsp dried)

• Salt and pepper

• Optional: a splash of coconut milk or crème fraîche for creaminess and a bed of spinach

Instructions:

1. Heat olive oil in a pan and gently cook the salmon fillets skin-side down for 4–5 minutes.

2. Flip and cook for another 3 minutes until lightly golden.

3. In the same pan, add mushrooms and garlic. Sauté for 3–4 minutes until soft.

4. Stir through lemon juice, dill and optional cream.

5. Season well and serve everything together with greens or a simple salad.

This is one of the easiest ways to naturally support vitamin D intake while keeping meals gut-friendly and nourishing.

My Functional Nutrition Approach

When clients come to me with fatigue, mood changes or immune concerns, I look at the bigger picture, not just symptoms in isolation. My approach blends:

• Functional testing

• Gut health support

• Hormone balancing

• Personalised nutrition

• Lifestyle tweaks that are realistic and sustainable.

Vitamin D is often just one piece of the puzzle, but it can be a powerful one.

If You’re Struggling With Energy, Mood or Immunity…

You don’t have to guess what your body needs.You don’t have to push through. And you don’t have to do it alone. If this sounds like you, let’s look at what’s really going on and create a plan that works for your body.

Book a free chat below and let’s talk through your symptoms, your goals and how we can get you feeling like yourself again.

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Lisa Claire - Nutritional Therapist

I’m Lisa Claire, a qualified, registered Nutritionist and Nutritional Therapist with a special interest in gut health, hormonal imbalances, sustainable weight loss and fatigue. I work one-to-one with individuals to uncover the root causes of their symptoms and create personalised nutrition, lifestyle and wellness plans that fit seamlessly into their lifestyles. Whether you’re struggling with digestive issues, hormonal imbalances or fatigue, I’m here to guide you toward lasting health transformations. Let’s work together to help you feel like you again.