Vitamin D Deficiency in Saudi Arabia: The Numbers
A comprehensive Saudi retrospective study spanning five years (2017-2021) found that 67.3% of subjects were below the adequate level for vitamin D (less than 30 ng/mL)[1]. Of these, 35.9% were in the deficient range, and 28.1% in the insufficient range. Females were more affected at 69.5% compared to 30.5% for males, and the 10-19 age group recorded the lowest average.
In the Eastern Province, a more recent study at the Maternity and Children Hospital in Dammam observed a gradual decrease from 51.8% in 2023 to 47.7% in 2025[2]. This improvement is noteworthy, yet half of the patients remain below sufficiency.
The wonder isn't that some Saudis lack vitamin D. It's that the majority of us are below sufficiency, with our sun shining 300 days a year.
Six Reasons for Deficiency Despite the Sun
The paradox isn't the absence of sun, but the barrier between us and it. Six factors work in concert:
1. The Heat Drives Us Indoors, Not Out. Summer temperatures in Riyadh and Jeddah can exceed 40°C, limiting natural outdoor activity to dawn and dusk hours, when UVB rays are insufficient.
2. Air Conditioning Keeps Us Captive for Nine Months. Modern life in the Kingdom revolves around air-conditioned homes, cars, and offices. Daily sun exposure might be limited to a few minutes walking between the car and the door.
3. Glass Blocks Rays. UVB rays responsible for vitamin D synthesis in the skin do not penetrate ordinary glass[3]. Sitting near a closed window produces nothing.
4. Clothing Covers Up. Full abayas, long robes, and dark clothing reduce the exposed skin area to less than 10% for many.
5. Sunscreen Reflects. SPF 30 blocks about 97% of UVB. Daily use, while beneficial against skin cancer, significantly reduces natural synthesis.
6. Winter Weakens the Sun, Even in the Tropics. The sun's angle in December and January makes UVB weaker. Saudi seasonal studies have found a decrease in levels during the colder months.
Signs of Deficiency: A Quick Self-Check
Deficiency doesn't shout. It manifests as daily complaints we attribute to other causes. Eight signs most associated with vitamin D deficiency, according to clinical reviews[4]:
Quick Self-Check
Select the symptoms that apply to you in the past four weeks:
Having three or more symptoms doesn't diagnose deficiency but signals the need for testing. Actual diagnosis comes from a single number in your blood.
Risks of Neglecting Deficiency
Chronic deficiency doesn't remain silent forever. Accumulation over years opens several doors:
- Osteoporosis and Fractures. Vitamin D regulates calcium absorption. Its absence gradually depletes bones, making hip fractures more likely after age 50.
- Weakened Immunity. Recent studies link deficiency to increased respiratory infections and frequent colds[5].
- Mood and Depression. Seasonal affective disorder is linked to vitamin D deficiency, though the causal relationship is still debated.
- Type 2 Diabetes. The Endocrine Society 2024 issued a clear recommendation to administer vitamin D to individuals with prediabetes to slow progression to full diabetes[6].
- Pregnancy and Postpartum. Deficiency in pregnant women is linked to fetal growth issues, gestational hypertension, and gestational diabetes.
- Child Development. Rickets, though rare today, is still recorded in the Kingdom in cases of severe infant deficiency.
Vitamin D Testing: How to Read Your Results
The test is called 25-hydroxyvitamin D or 25(OH)D. This reflects your blood reservoir and is the global standard. Do not confuse it with 1,25(OH)₂D; the latter is the active, short-lived form and does not indicate reservoir levels.
Levels according to the Endocrine Society and SFDA[7]:
Additional tests often requested with 25(OH)D when severe deficiency is suspected include: calcium, phosphate, parathyroid hormone (PTH), and alkaline phosphatase (ALP). Together, these provide a complete picture of calcium metabolism.
When to re-test after starting treatment? The answer: 8 to 12 weeks. This duration is sufficient to see a true response; less time may yield unrepresentative readings.
Sun Exposure: How Much Do You Really Need
The golden rule: 10 to 30 minutes of exposure, 3 to 4 days a week, between 10 AM and 3 PM. Only these hours contain effective UVB at our latitude. Before 10 AM and after 3 PM, the sun's angle is too oblique, and UVB is weak.
Duration varies based on skin tone and exposed area:
| Skin Tone | Daily Duration | Exposed Area |
|---|---|---|
| Fair | 10 - 15 minutes | Hands and forearms |
| Medium | 15 - 20 minutes | Hands, forearms, and face |
| Dark | 20 - 30 minutes | Hands, forearms, and face |
How Vitamin D Is Formed: From Your Skin to Your Supplement
Before choosing between salmon and a capsule, it's useful to understand vitamin D's journey: how it's created in your body, and where the active ingredient in the pill you buy comes from. This understanding explains why sun is primary, why D3 is better than D2, and why failing kidneys create deficiency even with adequate sun.
First: The Four Stages in Your Body
Vitamin D's journey from your skin to your cells involves four stages, with magnesium acting as a mediator in each.
-
1
Skin
Initial StageUVBrays convert7-dehydrocholesterolin the skin to previtamin D3, which then stabilizes into cholecalciferol (D3).Details
Requires specific
UVBwavelengths (290-315 nm). This wavelength does not penetrate ordinary glass, explaining why sitting near a closed window yields no vitamin D. Darker skin requires longer exposure to produce the same amount. -
2
Liver
First ConversionThe liver takes D3 and adds a hydroxyl group to become 25(OH)D (calcidiol), the form circulating in your blood and measured by tests.
Details
This is why the
25(OH)Dtest is the gold standard. It reflects a reservoir of weeks, not hours. A compromised liver (hepatitis, fatty liver, cirrhosis) slows this step, creating apparent deficiency even with sufficient sun. -
3