Vitamin D Deficiency: 9 Signs You're Running Low

Short answer: What do vitamin D deficiency symptoms look like?

Many people with low vitamin D have no clear symptoms, but common signs include persistent tiredness, muscle weakness, bone aches or tenderness, and an increased tendency to get colds and respiratory infections. These vitamin D deficiency symptoms should prompt testing (serum 25-hydroxyvitamin D) and a conversation about whether vitamin D supplements are appropriate (Forrest & Stuhldreher, Nutrition Research 2011; Aranow et al., Journal of Investigative Medicine 2011).

What is vitamin D deficiency?

Vitamin D deficiency means circulating 25-hydroxyvitamin D (25(OH)D) levels are lower than recommended for bone and immune health. Definitions vary slightly by guideline, but many researchers use <20 ng/mL (50 nmol/L) as the cutoff for deficiency (Holick et al., J Clin Endocrinol Metab 2011; Forrest & Stuhldreher, Nutrition Research 2011).

How common is low vitamin D?

Large surveys show low vitamin D is widespread. One U.S. analysis estimated about 41.6% of adults have 25(OH)D <20 ng/mL, making this one of the most common nutritional shortfalls (Forrest & Stuhldreher, Nutrition Research 2011). Prevalence varies by season, latitude, skin pigmentation, and lifestyle.

9 signs you may be running low on vitamin D

Below are nine low vitamin D signs people report most often. Any single sign can have many causes; use symptoms to guide testing and discussion with a clinician rather than to self-diagnose.

1) Persistent fatigue or low energy

Unexplained tiredness is often reported with low vitamin D. Observational studies link lower 25(OH)D with greater fatigue and lower self-rated health, though fatigue is non-specific and requires broader evaluation (Holick et al., J Clin Endocrinol Metab 2011).

2) Muscle weakness or aches

Vitamin D plays a role in muscle function; deficiency can present as weakness, especially proximal muscles (thighs, hips). Several trials suggest supplementation may improve muscle strength in deficient adults (Holick et al., J Clin Endocrinol Metab 2011).

3) Bone pain or tenderness

Low vitamin D reduces calcium absorption and can be associated with bone pain, particularly in the lower back, hips, or legs. Adults with low levels sometimes describe diffuse bone discomfort that improves after repletion (Holick et al., NEJM 2007).

4) Frequent colds, flu, or respiratory infections

Vitamin D receptors are present on nearly all immune cells, and low levels have been linked with higher rates of respiratory infections in several studies; randomized trials show mixed but promising results for supplementation reducing risk in deficient people (Aranow et al., Journal of Investigative Medicine 2011; Martineau et al., BMJ 2017).

5) Slow wound healing

Some research suggests vitamin D helps regulate inflammation and tissue repair; low levels have been associated with slower healing after surgery or injury (Holick et al., J Clin Endocrinol Metab 2011).

6) Bone fractures or low bone density

Chronic deficiency can contribute to low bone mineral density and increase fracture risk, especially in older adults. Clinical guidelines emphasize maintaining adequate vitamin D for bone health (Holick et al., J Clin Endocrinol Metab 2011).

7) Mood changes

Lower vitamin D levels have been observed in people with depressive symptoms in observational studies. While causality remains uncertain, some trials report small mood benefits from repletion in people who are deficient (Anglin et al., Br J Psychiatry 2013; Holick et al., 2011).

8) Hair thinning

Severe deficiency has been associated with hair loss conditions in some reports; mechanisms aren’t fully settled, and hair thinning has many possible causes (Holick et al., NEJM 2007).

9) Problems in women’s health (menstrual irregularity, bone concerns)

Women with low vitamin D may be more likely to report pelvic or bone pain and—through effects on bone—face higher osteoporosis risk later in life. Women with restricted diets (including some vegans) or absorption issues are particularly at risk; for broader context on multivitamin needs see our women's multivitamin guide and on common shortfalls see nutrient deficiencies in women (Allen et al., American Journal of Clinical Nutrition 2009; Forrest & Stuhldreher, Nutrition Research 2011).

Who is most likely to have low vitamin D?

Key risk groups include people with darker skin, those who cover their skin for cultural or medical reasons, people living at high latitudes, older adults, people with obesity, people who spend little time outdoors, and those with malabsorption (for example, celiac disease or bariatric surgery) (Forrest & Stuhldreher, Nutrition Research 2011; Aranow et al., Journal of Investigative Medicine 2011).

How is vitamin D status tested?

Status is assessed with a blood test for serum 25-hydroxyvitamin D (25(OH)D). This test reflects vitamin D made in skin and obtained from food and supplements and is the standard measure used in research and clinical care (Holick et al., J Clin Endocrinol Metab 2011).

When should someone consider vitamin D supplements?

Supplements may be reasonable for people with confirmed deficiency, those at high risk who cannot get adequate sun or dietary vitamin D, or when a clinician advises repletion. Randomized trials show the benefit is clearest for bone and in people who start with low levels; evidence for broader outcomes is mixed and often depends on baseline status (Holick et al., J Clin Endocrinol Metab 2011; Martineau et al., BMJ 2017).

Which form and dose: vitamin D3 vs. D2?

Cholecalciferol (vitamin D3) is the most commonly studied and tends to raise 25(OH)D levels more effectively than ergocalciferol (vitamin D2) at the same dose (Tripkovic et al., Am J Clin Nutr 2012). Typical repletion strategies vary: many clinicians use 1,000–4,000 IU/day for maintenance, while short courses of higher dosing are used under supervision; individual needs depend on baseline level, body size, and absorption (Holick et al., J Clin Endocrinol Metab 2011).

Are vitamin D supplements safe?

Vitamin D supplements are safe for most people when used at recommended doses. Toxicity is rare and usually involves very high intakes over time leading to high calcium levels; keeping to guideline-based dosing and monitoring levels when taking high doses reduces risk (Institute of Medicine, 2011; Holick et al., J Clin Endocrinol Metab 2011).

Food sources and sun exposure: how to build vitamin D naturally

Natural food sources include fatty fish (salmon, mackerel), fortified dairy or plant milks, and egg yolks; however, food alone often provides limited vitamin D for people with low levels. Sun exposure produces vitamin D in skin, but safe sun practices, latitude, season, and skin pigmentation all influence how much is synthesized (Holick et al., NEJM 2007).

Testing, re-testing, and working with your clinician

If symptoms or risk factors suggest deficiency, a clinician can order a baseline 25(OH)D test. If supplements are started to correct deficiency, recheck levels after 8–12 weeks of consistent dosing to confirm response and adjust dose as needed (Holick et al., J Clin Endocrinol Metab 2011).

Special considerations for women

Women of childbearing age, pregnant people, and older women have unique bone-health considerations. Pregnant people may have increased needs, and older women face higher fracture risk; discussing vitamin D alongside overall nutrient intake is important. For a broader look at daily multivitamin options and how they fit into women’s health, see our women's multivitamin guide and the article on nutrient deficiencies in women (Allen et al., American Journal of Clinical Nutrition 2009).

How supplements vitamin D3 compare to taking a multivitamin

Single-nutrient vitamin D3 supplements are useful when a clear deficiency is identified. Daily multivitamins that include vitamin D can be convenient for general coverage, especially when paired with other nutrients that support bone health. Choose third-party tested products and check label dose to match your clinician’s recommendation (Forrest & Stuhldreher, Nutrition Research 2011).

Practical takeaways and next steps

• If you have persistent fatigue, muscle weakness, bone pain, frequent infections, or risk factors above, ask your clinician about a 25(OH)D test (Forrest & Stuhldreher, Nutrition Research 2011).
• If levels are low, cholecalciferol (vitamin D3) is the preferred form for repletion; dosing should be individualized and follow clinical guidance (Holick et al., J Clin Endocrinol Metab 2011).
• Combine sensible sun exposure, dietary sources, and supplements when recommended. Monitor levels if taking higher doses.

For people who prefer a once-daily routine and broad nutrient coverage, a high-quality multivitamin can simplify adherence. One science-minded option is Go Wise Multivitamin, a comprehensive daily multivitamin in convenient stick-pack format — no water needed, easy to take anywhere. It offers travel-friendly, vegan and gluten-free, third-party tested coverage that may help bridge gaps when diet or sun exposure is limited (Allen et al., American Journal of Clinical Nutrition 2009).

Bottom line: vitamin D deficiency symptoms can be subtle. Testing is the reliable way to know your status and whether vitamin D supplements are appropriate. Talk with your healthcare provider to interpret results and choose a safe, evidence-based plan (Holick et al., J Clin Endocrinol Metab 2011; Aranow et al., Journal of Investigative Medicine 2011).

This article summarizes current research but does not replace personalized medical advice. Consult your clinician before starting supplements or changing your care plan.

Frequently Asked Questions

What are the most common vitamin D deficiency symptoms?

Common signs include persistent fatigue, muscle weakness, bone aches or tenderness, and more frequent respiratory infections. Because these symptoms are non-specific, a serum 25-hydroxyvitamin D test is the reliable way to determine deficiency (Forrest & Stuhldreher, Nutrition Research 2011; Holick et al., J Clin Endocrinol Metab 2011).

How is vitamin D deficiency tested?

A blood test measuring serum 25-hydroxyvitamin D (25(OH)D) is the standard test. Results guide whether supplements are needed and help clinicians tailor dose and follow-up (Holick et al., J Clin Endocrinol Metab 2011).

Should I take vitamin D supplements or a multivitamin?

If testing shows deficiency, targeted vitamin D3 supplements are often recommended to restore levels. For general coverage or travel convenience, a third-party tested multivitamin with vitamin D can be useful — discuss with your clinician to match dose to your needs (Forrest & Stuhldreher, Nutrition Research 2011).

How much vitamin D should I take?

Recommended maintenance doses commonly range from 1,000–4,000 IU/day depending on baseline levels, body size, and other factors. Higher therapeutic doses are sometimes used short-term under clinical supervision; monitoring 25(OH)D helps ensure safety (Holick et al., J Clin Endocrinol Metab 2011).

Are vitamin D supplements safe long-term?

When used at guideline-consistent doses and monitored when needed, vitamin D supplements are safe for most people. Toxicity is rare and usually tied to very high intakes over time; follow clinician guidance and recheck levels if taking high-dose therapy (Institute of Medicine 2011; Holick et al., 2011).