Vitamin D Deficiency Test: Risk and Symptoms

This test estimates how likely it is that vitamin D intake and skin synthesis fall short, based on everyday habits: season, age, skin type, time outdoors, diet, body mass index and supplement use. It takes about one minute: 8 questions and a list of common signs. The result is a risk self-check based on habits, not a diagnosis. Vitamin D status can only be confirmed with a blood test for 25(OH)D.

How the result is calculated

Points are added for known risk factors, and a regular supplement subtracts points. The season is set automatically from the current date. The total cannot go below 0.

Factor	Answer	Points
Season (from the date)	October to March	+3
	April and September	+1
	May to August	0
Age	18–64 years	0
	65–74 years	+1
	75 years and older	+2
Skin reaction to the first summer sun	Burns easily	0
	Burns, then tans	0
	Tans quickly	+1
	Hardly burns, dark skin	+2
Summer outdoors for at least 15 minutes a day with face and arms uncovered	4 or more days a week	0
	1–3 days a week	+1
	Almost never	+2
SPF 30+ sunscreen used most often, or skin covered	Yes	+1
Oily fish (herring, salmon, mackerel, sprats)	2 or more times a week	0
	About once a week	+1
	Less often	+2
Eggs and foods fortified with vitamin D	Several times a week	0
	Rarely	+1
Body mass index (BMI) of 30 or more	Yes (if unknown, 0)	+2
Vitamin D supplement of 10 µg or more	Almost daily	minus 4
	Sometimes	minus 2

The total gives one of three results:

• 0–4 points: lower risk.
• 5–8 points: medium risk.
• 9 points or more: higher risk.

Risk here means the chance that intake and skin synthesis do not reach the amount recommended by EFSA. The list of signs is not included in the score. It only shows how many common signs were ticked.

The points are an expert model built on known risk factors (EFSA, NIH ODS). It is not a validated clinical questionnaire and cannot show the actual vitamin D level.

Why these factors are asked about

Season reflects how much sun reaches the skin. Age, skin type, time outdoors and sunscreen or clothing describe how much vitamin D the skin can make when the sun is strong enough. Oily fish, eggs and fortified foods show how much comes from diet. A body mass index of 30 or more is included because obesity is linked to a lower 25(OH)D concentration. A regular supplement adds to intake, so it subtracts points.

A lower-risk result does not rule out a deficiency, and a higher-risk result does not confirm one. The score only sorts habits into groups to show where a closer look is worthwhile.

Why vitamin D runs low in Lithuania in winter

Lithuania lies between 54° and 56° north. In measurements at 42° and 52° north (Webb et al., 1988), winter sunlight produced little vitamin D in the skin. At Lithuania's latitude the sun stays too low for the skin to make a meaningful amount roughly from October to March. In these months, food and supplements are the main sources.

Summer sun does not guarantee a sufficient level either. Synthesis falls when most of the day is spent indoors, when clothing covers the skin, and when sunscreen is applied. Darker skin needs longer in the sun to make the same amount. The skin of older people produces less vitamin D. Obesity is linked to a lower 25(OH)D concentration (Wortsman et al., 2000).

How much vitamin D is needed

EFSA (2016) set an adequate intake for adults of 15 µg (600 IU) per day, assuming minimal skin synthesis. The tolerable upper intake level for adults is 100 µg (4,000 IU) per day. The conversion is simple: 1 µg equals 40 IU. Labels on foods and supplements give the amount in µg or IU, so the ratio is worth knowing. In winter, when skin synthesis is close to zero, intake from food and supplements is the main source of vitamin D.

Vitamin D in food

The table lists common sources with the amount per serving (NIH ODS).

Food and serving	Vitamin D, µg	Vitamin D, IU
Cod liver oil, 1 tablespoon	34	1,360
Rainbow trout, farmed, cooked, 85 g	16.2	645
Sockeye salmon, cooked, 85 g	14.2	570
Mushrooms exposed to UV light, ½ cup	9.2	366
Milk fortified with vitamin D, 1 cup	2.9	120
Fortified plant-based drinks, 1 cup	2.5–3.6	100–144
Sardines in oil, 2 fish	1.2	46
Egg, 1 large	1.1	44
Tuna in its own juice, 85 g	1.0	40

Without oily fish or fortified foods, reaching 15 µg a day from diet alone is difficult. The table shows that oily fish and cod liver oil contain far more vitamin D than eggs or tuna, and a single serving of a fortified drink or milk does not cover the 15 µg figure.

25(OH)D blood test

Vitamin D status is shown by the blood concentration of 25(OH)D. NIH ODS describes the ranges like this:

• below 30 nmol/l (12 ng/ml): deficiency;
• 30–50 nmol/l (12–20 ng/ml): may be inadequate;
• 50 nmol/l (20 ng/ml) and above: adequate for most people;
• above 125 nmol/l (50 ng/ml): linked to possible adverse effects.

The unit conversion is 1 ng/ml = 2.5 nmol/l. The test can be done at a laboratory, and the result is best discussed with a doctor.

Signs linked to vitamin D deficiency

Several signs are associated with low vitamin D:

• fatigue;
• muscle weakness or pain;
• bone pain;
• low mood in the dark months;
• frequent colds.

These signs are nonspecific. Each has many other causes, and a deficiency often causes no signs at all. Only a blood test can establish it.

When to see a doctor

Medical advice is appropriate for severe or long-lasting bone pain, fractures without a clear cause, and for people who take regular medication or have a chronic illness.

What to do based on the result

• Lower risk: current habits look suitable. In winter it is worth reviewing the diet.
• Medium risk: more oily fish and fortified foods help, and a blood test makes sense when in doubt.
• Higher risk: a 25(OH)D test and a talk with a doctor or pharmacist about a supplement dose are advisable.

More than 100 µg a day should not be taken without a doctor's advice. The store carries vitamin D supplements for those who decide on one after that conversation.

Frequently asked questions

Does the test replace a blood test?

No. The test shows risk based on habits. Only a 25(OH)D blood test measures the actual level.

Why does the test ask about skin reaction to the sun?

Skin with more pigment makes vitamin D more slowly, so darker skin needs longer in the sun for the same amount. Reaction to the first summer sun is a simple way to estimate skin type.

Is enough vitamin D made from summer sun in Lithuania?

It depends on the time spent outdoors and how much skin is uncovered. Time indoors, clothing and sunscreen reduce synthesis.

Is it possible to get too much vitamin D?

Yes, mostly from supplements. The EFSA upper limit for adults is 100 µg (4,000 IU) per day.

Are the answers stored anywhere?

No. The result is calculated in the browser. Only the email address is stored.

Sources

1. EFSA (2016). Dietary reference values for vitamin D
2. EFSA (2023). Scientific opinion on the tolerable upper intake level for vitamin D
3. NIH Office of Dietary Supplements. Vitamin D Fact Sheet for Health Professionals
4. Webb AR, Kline L, Holick MF. J Clin Endocrinol Metab 1988
5. Wortsman J et al. Am J Clin Nutr 2000

Updated 2026–11–08. The test is an informational tool, not a medical diagnosis, and does not replace a consultation with a doctor.