Low Vitamin D3: symptoms and how to fix it
Vitamin D, often referred to as the “sunshine vitamin”, plays a central role in regulating calcium and phosphorus absorption, maintaining bone and muscle health, modulating the immune system, and—according to recent studies—potentially influencing mood.
This review focuses specifically on Vitamin D3 (cholecalciferol). We will examine the implications of low Vitamin D3 levels, the symptoms that should not be overlooked, consequences for specific conditions (such as pregnancy or mood disorders), reference values, strategies to increase levels, and finally, a spotlight on Cartial D, a product by Eidon Salus designed to support both Vitamin D3 and cartilage health.
What is Vitamin D3
Vitamin D3 (cholecalciferol) is the biologically active form of vitamin D, synthesized in the skin through exposure to UVB rays from sunlight and can also be obtained through dietary sources or supplementation.
. Its primary function is to support intestinal absorption of calcium and phosphorus, contributing to normal bone and muscle maintenance. Recent research suggests additional roles, including immune modulation, neuromuscular function, and potential influence on mood regulation.
. It is important to distinguish between “vitamin D” in general—which may refer to several forms—and Vitamin D3, the most biologically active form commonly used for supplementation.
Reference Values and What “Low Vitamin D3” Means
Vitamin D status is typically assessed by measuring circulating 25-hydroxyvitamin D (25(OH)D).
According to current guidelines and recent studies:
- Levels ≥ 50 nmol/L (≈ 20 ng/mL) are generally considered
- Values below this threshold are associated with adverse
- Some experts suggest that higher levels (e.g., >30 ng/mL) may provide additional benefits beyond bone health.
In summary, “low Vitamin D3” indicates a 25(OH)D concentration below the levels considered optimal for overall health.
Why Low Vitamin D3 Should Not Be Overlooked
Vitamin D3 deficiency may have multiple consequences:
- ● Bone health: Reduced mineralization, increased risk of osteopenia, osteoporosis, and fractures.
- ● Muscle function: Weakness, musculoskeletal pain, and reduced performance; in older adults, this can elevate the risk of falls.
- Immune function: Very low levels have been linked to increased susceptibility to infections.
- ● Mood and mental well-being: Deficiency has been associated with depressive or anxious symptoms.
Typical Symptoms of Low Vitamin D3
Although often nonspecific, recognizing early signs is important for timely intervention:
- Fatigue and low energy: Persistent tiredness not explained by
- Muscle and bone pain, weakness: Particularly in proximal muscles and generalized skeletal discomfort.
- Sleep disturbances: Difficulty falling asleep or frequent nighttime awakenings may be linked to low Vitamin D.
- Mood changes: Low Vitamin D has been associated with depressive or anxious
- Increased incidence of infections or recurrent malaise: Reflecting its role in immune
Low Vitamin D3 and Depression
In recent years, the relationship between Vitamin D3 and mental health has been extensively investigated. A meta-analysis demonstrated that individuals with lower 25(OH)D levels had a significantly higher risk of depression (hazard ratio approximately 2.21 for the lowest versus highest levels).
However, interventional studies provide less definitive results. For instance, in a randomized trial involving over 18,000 adults without depression at baseline, supplementation with Vitamin D3 did not significantly reduce the risk of developing depression compared to placebo.
Other recent studies have shown that supplementation may reduce depression scores in individuals who were already depressed.
There is a solid association between low Vitamin D3 and depression, but causality and the effectiveness of supplementation as a therapeutic measure remain partially unclear.
Low Vitamin D3 During Pregnancy
Pregnancy requires particular attention regarding Vitamin D status. Women with low Vitamin D levels are at increased risk for complications such as pre-eclampsia, low birth weight, and impaired fetal bone mineralization.
Official guidelines recommend supplementation considered safe at 1,000–2,000 IU/day if deficiency is identified.
Some studies suggest that doses up to 4,000 IU/day are safe and may be necessary to normalize very low levels. Pregnant women should therefore assess their Vitamin D status in consultation with their obstetrician and consider supplementation when indicated.
Specific Symptoms: Vitamin D Deficiency and Fatigue
Fatigue is one of the most frequently reported symptoms of Vitamin D deficiency. This is because Vitamin D3 plays a role in muscle function, sleep quality, and mood regulation.
Fatigue due to Vitamin D deficiency is often misattributed to ordinary “daily tiredness,” but if it is persistent and accompanied by other signs—such as muscle pain, low mood, or disturbed sleep—it may indicate the need to assess 25-hydroxyvitamin D (25-OH-D) levels.
How to Increase Vitamin D3
The main strategies include:
- Sun Exposure – Stimulate cutaneous Vitamin D3 production via UVB rays: approximately 10–30 minutes of direct sunlight on the face, arms, and legs, multiple times per Duration depends on season, latitude, skin pigmentation, and use of sunscreen.
- Diet – Consume foods rich or fortified with Vitamin D: fatty fish (salmon, mackerel), cod liver oil, eggs, UV-exposed mushrooms, fortified milk or plant-based
- Supplementation – Indicated in documented deficiency or higher-risk groups (e.g., pregnant women, limited sun exposure, darker skin, obesity, malabsorption). Guidelines suggest 600–2,000 IU/day for many healthy adults, while higher doses may be necessary for confirmed deficiency, always under medical supervision.
- Clinical Monitoring – Blood measurement of 25-OH-D to confirm adequacy and monitor the effectiveness of the chosen intervention.
Difference Between Vitamin D3 and Generic “Vitamin D”
The term “Vitamin D” is often used generically, but it actually encompasses multiple forms:
- Vitamin D2 (ergocalciferol) and Vitamin D3 (cholecalciferol).
- D3 is the endogenous form produced in the skin and is generally considered more effective at raising blood levels compared to D2.
- In supplements and clinical studies, D3 is the preferred form for correcting
Thus, when referring to “low Vitamin D3,” the focus is specifically on this form and its physiological impact.
Vitamin D3 Supplements: Key Considerations
When selecting a Vitamin D3 supplement, consider:
- Form: Colecalciferol (D3).
- Dosage: Tailored to individual needs based on age, clinical status, and sun
- Administration schedule: Daily or periodic
- Combination with other nutrients: Calcium, magnesium, and vitamin K2 may provide synergistic effects.
- Product quality: Check certifications, transparency of concentration, and manufacturing standards.
In the context of joint care and musculoskeletal wellness, Cartial D by Eidon Salus represents an interesting combined approach. It contains hydrolyzed hyaluronic acid at 6% in a sublingual form (low molecular weight: 40 kDa) to support synovial absorption, along with Vitamin D3 (cholecalciferol) at 500 IU per ml.
This dual-action formulation may be beneficial in cases of osteoarthritis, post-traumatic situations, tendon complications in athletes, post-injection hyaluronic acid therapy, and osteoporosis.
Thanks to the inclusion of Vitamin D3, Cartial D can contribute not only to the support of cartilage and synovial fluid,but also to the restoration of Vitamin D3 levels, which is crucial for bone, muscle, and joint health.
It is important to note that, although it is a dietary supplement, Cartial D should be used as part of a broader healthy lifestyle, including sun exposure, balanced nutrition, and physical activity, and always under medical supervision.
Conclusion
Maintaining adequate vitamin D3 levels is not only essential for “healthy bones” but is also part of a broader wellness perspective: stronger muscles, a more efficient immune system, better sleep quality, and a potential positive impact on mood.
If you suspect low vitamin D3—due to persistent fatigue, muscle pain, low mood, risk conditions such as pregnancy, or limited sun exposure—it is advisable to measure your 25(OH)D levels and intervene promptly if necessary.
Supplementation through targeted diet, increased sun exposure, and, when indicated, a high-quality product such as Cartial D can make a significant difference.
Remember: each individual is unique, and personalized medical evaluation remains essential.
FAQ
Normally, a value of 25(OH)D ≥ 50 nmol/L (≈ 20 ng/mL) is considered sufficient. Some guidelines point to >30 ng/mL for optimization. PMC+1
Risks include osteoporosis, fractures, reduced muscle function, potentially higher susceptibility to infections, and possible associations with depressed or anxious mood.
It depends on latitude, season, skin pigmentation, and sunscreen use. Generally, 10–30 minutes of direct sunlight on the face, arms, and legs several times per week during favorable months is recommended.
A high-quality vitamin D3 (colecalciferol) supplement with appropriate dosage and medical supervision is usually sufficient. In specific cases, such as osteoarthritis combined with deficiency, a combined formulation like Cartial D may be beneficial.
Yes. Pregnant women are at higher risk. Guidelines recommend supplementation of 1,000–2,000 IU/day if deficiency is identified, and some studies suggest doses up to 4,000 IU/day may be safe.
