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At-home vitamin D test: who needs one and what the levels mean

By the Life in Good Form editors. Updated 2026-10-15.

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What a vitamin D test measures

MedlinePlus explains that before your body can use vitamin D, your liver changes it into 25 hydroxyvitamin D, or 25(OH)D, and most vitamin D blood tests measure that form because it is the most accurate way to see if you have enough. Results may be reported as total vitamin D or as separate D2 and D3 amounts; MedlinePlus says total vitamin D is the important number.

A different test for active vitamin D, also called calcitriol, is not usually used to check whether you have enough, MedlinePlus says.

What your level means

ODS notes that one nmol/L equals 0.4 ng/mL, so check which unit your kit reports. Your result may also be labeled deficient, insufficient, sufficient or toxic, MedlinePlus says. Talk with your provider about what your number means for you.

Who may need testing

MedlinePlus says routine testing is not recommended for everyone, and a provider may order one if you have a condition linked to deficiency, such as osteomalacia, low bone density or rickets, or symptoms such as bone pain, muscle weakness or fractures. Your risk may also be higher if you:

• Rarely expose your skin to sunlight, stay indoors, cover up or use sunscreen outside.
• Have had weight loss surgery, or have Crohn's disease, ulcerative colitis or celiac disease.
• Have kidney or liver disease that affects how you convert vitamin D.
• Take medicines that affect vitamin D, including certain statins, steroids and weight-loss medicines.

ODS adds that older adults and people with dark skin make less vitamin D from sunlight, and that almost one out of four people in the United States have levels that are too low or inadequate.

For babies, ODS says breast milk alone does not provide enough vitamin D and that breastfed infants should get a supplement of 10 mcg (400 IU) a day. MedlinePlus adds that a provider may test babies who are mainly breastfed and children whose diets are low in vitamin D; see our infant vitamin D drops guide.

Too much vitamin D

ODS says very high blood levels, greater than 375 nmol/L (150 ng/mL), can cause nausea, vomiting, muscle weakness, confusion, pain, loss of appetite, dehydration, excessive urination and thirst, and kidney stones. High levels are almost always caused by taking too much from supplements, and you cannot get too much from sunshine, ODS says.

ODS lists an upper limit of 100 mcg (4,000 IU) a day for adults 19 and older from all sources, though your provider might recommend more for a time to treat a deficiency. MedlinePlus says that if your level is high or toxic, you will need to stop the supplements.

Using a home kit

• Tell your provider what you take. MedlinePlus says medicines, vitamins and supplements may affect results, but do not stop any medicine on your own.
• No fasting needed. MedlinePlus says you do not need special preparation for a vitamin D test.
• Check the units. Compare your number against the right column of the ODS ranges.
• Retest only when useful. MedlinePlus says providers may retest people taking supplements for a deficiency to see if levels are improving.

If your level is low

MedlinePlus says a provider may recommend vitamin D supplements or more vitamin D rich foods, and that this is usually safer than more sun, which may cause skin cancer. Only a few foods, such as egg yolks, liver and fatty fish, naturally contain vitamin D, so it is added to many foods such as milk and breakfast cereals. ODS says vitamin D is best absorbed with a meal or snack that includes some fat.

For supplement choices, see our vitamin D3 1,000 IU guide, liquid vitamin D drops guide and calcium with vitamin D guide.

What to look for when you buy

Questions people ask

What is a normal vitamin D level?

ODS says 50 nmol/L (20 ng/mL) or above is adequate for most people.

What vitamin D level is too low?

ODS says below 30 nmol/L (12 ng/mL) is too low and might weaken your bones.

Should everyone test their vitamin D?

No. MedlinePlus says routine vitamin D testing is not recommended for everyone.

Do I need to fast for a vitamin D test?

MedlinePlus says no special preparation is needed, but tell your provider what you take.

Can you get too much vitamin D?

Yes, from supplements. ODS says you cannot get too much from sunshine.

Sources

• Vitamin D Test (medlineplus.gov), MedlinePlus, U.S. National Library of Medicine
• Vitamin D: Fact Sheet for Consumers (ods.od.nih.gov), NIH Office of Dietary Supplements

Sources checked 2026-10-15.