Vitamin D Deficiency Symptoms: How to Tell

Differences Between Vitamin D Insufficiency and Deficiency

While both terms are commonly associated with low levels of vitamin D, there are distinct differences between the two. These distinctions affect the degree to which your symptoms will manifest themselves, and how aggressive you’ll need to be to resolve the issue.

The Endocrine Society has established the following standards based upon measurements of 25(OH)D (the standard blood marker):

• Sufficient: 30 ng/mL (75 nmol/L) or greater
• Insufficient: 20-29 ng/mL (50-72 nmol/L)
• Deficient: less than 20 ng/mL (less than 50 nmol/L)
• Severely deficient: less than 12 ng/mL (less than 30 nmol/L)

One of the problems with determining insufficiency is that it falls within a gray area. Your level is not low enough to cause obviously apparent clinical signs such as weakened bones or severe muscle wasting, but your body isn’t performing at its best. As a consequence, the symptoms caused by this condition will generally be somewhat vague: mild fatigue, a slight decrease in mood, a bit more time required to recover from physical activities.

As levels continue to decline and move toward true deficiency and severe deficiency, symptoms will begin to become difficult to ignore. Bone pain, noticeable weakness, repeated illnesses, and marked decreases in mood start to appear.

An estimated 1 billion people worldwide have insufficient or deficient vitamin D levels according to a 2020 narrative review of the current global status. Unfortunately, the vast majority of deficient individuals, remain unaware.

7 Symptoms of Low Vitamin D

The range from insufficiency to deficiency determines the magnitude of the symptoms. The main difference is the intensity: insufficiency leads to milder forms of each symptom that are easy to attribute to another factor, whereas deficiency creates more intense forms that become increasingly difficult to ignore.

Ongoing Fatigue Regardless of Rest

Many people initially dismiss fatigue as the first sign of low vitamin D. Although you get a good night’s sleep (typically 7-8 hours), you’re fatigued again by mid-afternoon. It is very easy to attribute fatigue to either work-related stress or simply having a bad night’s sleep. But when your fatigue is continuous and doesn’t improve regardless of rest, low vitamin D is likely a contributing factor.

A randomized double-blind study of 120 participants demonstrated that one dose of vitamin D resulted in significant improvement in fatigue ratings compared to placebo in otherwise healthy adults who were deficient. Since fatigue improved after only one dose in a controlled environment, it is unlikely that this occurred coincidentally.

Bone Pain and Lower Back Discomfort

Vitamin D directly influences how much calcium is absorbed into your bones. With decreasing levels, your bones gradually lose their ability to hold onto minerals, resulting in a dull, achy pain. Typically this occurs in your lower back, hips, or legs.

This form of pain is fundamentally different from a muscle strain or an injury. It tends to be present all the time rather than sharp, it worsens at night, and it cannot be traced back to any identifiable physical activity you performed.

Muscle Weakness, Especially in the Legs and Hips

When we refer to muscle weakness here, we’re referring to something more than just general fatigue. We’re discussing a state where you find yourself being exhausted climbing stairs, needing assistance getting out of a low chair, or finding that previous exercise routines are more difficult than expected.

There are vitamin D receptors located throughout skeletal muscle tissue. Vitamin D deficiency causes what clinicians call proximal myopathy, a pattern of weakness that affects muscles closest to the trunk first, particularly the hips and thighs. This is why your legs feel heavy climbing stairs or you struggle to stand from a low chair before you notice weakness anywhere else. Deficiency also causes preferential atrophy of type II (fast-twitch) fibers, which are responsible for quick, powerful movements like catching your balance or pushing off the ground.

Getting Sick More Often Than Usual

If you’re catching a cold every couple of months, it’s likely vitamin D has something to do with it. There is evidence supporting that vitamin D functions directly in the activation of immune cells tasked with fighting invading pathogens, especially within the respiratory tract.

Researchers conducted a large individual participant meta-analysis combining data from 25 randomized controlled trials and 11,321 participants, demonstrating that supplementing with vitamin D resulted in a statistically significant decrease in incidence of acute respiratory infections. The greatest impact was observed in cases where subjects started with severe deficiency at baseline (25(OH)D below 25 nmol/L), with a nearly 70% reduction in infections.

Low Mood or Seasonal Depression

It is well known that many people experience a dip in mood during the winter months. This has an understandable biological basis: vitamin D receptors exist in regions of the brain responsible for regulating mood, and multiple studies demonstrate that decreased levels of vitamin D correlate with depressive symptoms.

A meta-analysis of 14 studies totaling 31,424 participants demonstrated that individuals with lower levels of vitamin D exhibited significantly higher rates of depression relative to those whose levels were sufficient. The correlation was strongest within the cross-sectional studies, with an odds ratio of 1.31 for the lowest compared to highest vitamin D categories.

Decreased mood may be caused by numerous factors. But if your mood drops noticeably during autumn and winter, or you frequently feel flat without clear justification, testing your vitamin D levels may be warranted.

Slow Wound Healing

Vitamin D is part of how your body produces the substances that help create new skin when you suffer a cut, scrape, or have surgery. It controls inflammation around the injury area as well. If there’s a lack of sufficient vitamin D, you may find it takes much longer for cuts, scrapes, and surgical wounds to close and fully heal than you might normally anticipate.

If you’ve observed that small injuries appear to remain open for several weeks, or that bruising fades significantly slower than normal, this too may represent additional evidence of low vitamin D.

Hair Thinning or Increased Shedding

There are vitamin D receptors present within hair follicle cells, and they are needed for the normal functioning of the hair growth cycle. If these receptors are unable to receive adequate amounts of vitamin D, the cycle may become disordered, leading to excessive shedding or diffuse thinning.

Research has found an inverse correlation between vitamin D levels and non-scarring hair loss conditions such as alopecia areata, telogen effluvium, and androgenetic alopecia. Approximately half of those diagnosed with these conditions have been found to be vitamin D deficient.

Hair loss can result from multiple factors, so low vitamin D by itself may not entirely explain the thinning. But if it occurs simultaneously with other symptoms on this list, the likelihood that it is a contributing factor, is higher.

Who Is Most at Risk for Low Vitamin D

Many people are at increased risk of having suboptimal vitamin D levels due to several factors that influence the body’s ability to create, absorb, or store the vitamin.

Reduced Skin Synthesis

Your skin creates vitamin D using the direct action of UVB light. Any factor that hinders this process will increase your risk:

• Darker skin pigmentation. Individuals with greater amounts of melanin require more sunlight to produce an equal amount of vitamin D compared to someone with lighter skin
• Daily sunscreen use. SPF 30 blocks roughly 97% of UVB radiation, which is great for skin cancer prevention but significantly reduces vitamin D synthesis
• Living above 35 degrees north latitude. During winter months at these latitudes (roughly above Atlanta in the US, or above Crete in Europe), UVB exposure is insufficient for adequate vitamin D production
• Working indoors. Office workers and those with irregular schedules who spend little time outside during peak sun hours are at higher risk
• Older age. A 70-year-old produces approximately 75% less vitamin D under similar sunlight conditions compared to a 20-year-old

Reduced Absorption

Although there may be adequate amounts of vitamin D available through diet (rare) or supplementation, some health conditions limit the small intestine from effectively absorbing the nutrient:

• Celiac disease
• Crohn’s disease and inflammatory bowel disease
• Gastric bypass surgery or other procedures that decrease absorptive surface area
• Other gastrointestinal conditions that lead to chronic fat malabsorption, since vitamin D is fat-soluble and needs dietary fat for absorption

Increased Demand

• Obesity and higher body fat. Due to its fat solubility, vitamin D is “trapped” in adipose tissue and becomes unavailable in the bloodstream. Individuals with a BMI over 30 may require 2-3 times the standard dose to achieve equivalent blood levels
• Pregnancy and breastfeeding. The developing baby draws on the mother’s vitamin D reserves, greatly increasing demand

How to Confirm Low Vitamin D

The only confirmed method to determine your vitamin D level is a blood test measuring serum 25(OH)D. This represents the total amount of vitamin D produced by your liver from skin synthesis and gut absorption, and it reflects your total stores over the past 2-3 weeks.

A blood draw is all that is required for the test. Results usually take just a few days to arrive and show you exactly where you stand on the sufficiency scale described above.

You cannot safely rely upon symptoms alone. There are many possible causes for each symptom listed here, from thyroid problems to iron deficiency to simply needing more sleep. A blood test eliminates guessing entirely.

What to Do if You Suspect Low Vitamin D

First, get blood work done. Everything else is based on getting a real number.

When you get those results and find out you have low levels, it’s time to create a targeted supplementation plan based on just how deficient you are. We cover the specific protocols, dosing strategies, and timelines in our guide to fixing low vitamin D levels.

If you want to go for a food-based approach, fatty fish (salmon, mackerel, and sardines) are the best natural sources of vitamin D. But diet alone does not provide enough for most people. Our breakdown of foods high in vitamin D covers what to eat and how much you’ll actually get from it.

Before you start supplementing on your own, remember that there is a ceiling for vitamin D intake. More is not always better. Our guide on vitamin D toxicity explains how much is too much and what can happen if you overdo it.

For the bigger picture on what vitamin D does beyond treating a deficiency, our main vitamin D benefits article covers the full range. And if you’re ready to pick a supplement, we review the best options in our vitamin D supplement guide.