What vitamin D does

Vitamin D is a nutrient your body uses to absorb calcium from food. Without enough of it, bones can get soft and weak. In children this is called rickets. In adults it is called osteomalacia, and over time it can contribute to osteoporosis, where bones break easily.

Vitamin D also helps muscles work and plays a role in the immune system. Scientists are still studying how big that role is. Your body stores vitamin D in fat, so what you build up in summer can carry you partway through winter.

Where it comes from

Your skin makes vitamin D when sunlight hits it. That is why it is sometimes called the sunshine vitamin. But in New York and New Jersey, the sun is too weak from about November to March for your skin to make much. Sunscreen, dark skin, being indoors, and being older all lower how much you make.

Food gives you some. The best sources are fatty fish like salmon and sardines, egg yolks, and foods with vitamin D added, like milk, some orange juice, and some cereals. Most people do not get enough from food alone.

Supplements come in two forms: D2 and D3. D3 is the form your skin makes, and studies show it raises blood levels a bit more effectively than D2. Both are sold over the counter. Prescription-strength vitamin D (50,000 IU capsules) is also available for people who are very low.

How much you need

The National Institutes of Health (NIH) gives these daily targets: 600 IU for adults up to age 70, and 800 IU for adults over 70. The safe upper limit for adults is 4,000 IU a day unless a clinician tells you otherwise.

Taking far more than that for a long time can raise calcium in your blood too high. That can cause nausea, confusion, kidney stones, and heart rhythm problems. More is not always better.

Signs you might be low

Mild vitamin D deficiency usually has no obvious symptoms. That is why so many people do not know they are low. When symptoms do show up, they can include tiredness, bone or back pain, muscle aches or weakness, and getting sick more often.

People at higher risk include those who get little sun, have darker skin, are over 65, are overweight, have had weight-loss surgery, or have gut conditions like celiac or Crohn's disease that block absorption.

How testing works

The only way to know your level is a blood test called 25-hydroxyvitamin D. NIH describes levels below 12 ng/mL as deficient and 12 to 20 ng/mL as not enough for bone health. Many clinicians aim for 20 to 50 ng/mL.

The test is quick and simple. At Zen IV Spa, a licensed nurse can come to your home in New York or New Jersey to draw the blood, so there is no office wait. Results come back in a few days, and a clinician reviews them with you on a video visit.

What the big studies say

For years, people hoped vitamin D pills would prevent cancer, heart disease, and more. The largest test of that idea was the VITAL trial, published in the New England Journal of Medicine in 2019. It followed more than 25,000 adults for about five years. Daily vitamin D did not lower rates of cancer or heart attacks in people who were not deficient. A later report from the same trial found it did not reduce fractures in generally healthy adults either.

The takeaway: if you are truly low, fixing it matters for your bones and muscles. If your level is already fine, extra vitamin D likely does not add much. Testing tells you which group you are in.

How Zen IV Spa can help

If you suspect you are low, Zen IV Spa can draw your vitamin D and other labs at home. If you need prescription-strength vitamin D or other everyday medicines, Zen IV Spa's everyday prescriptions start at $79 per month and ship to your door after a video visit. Learn more at zenivspa.com/everyday-health/ or call (332) 239-2005.

Common Questions

Can I get enough vitamin D from the sun in New Jersey?+

In summer, usually yes with 10 to 30 minutes of midday sun a few times a week. From about November to March, the sun is too weak at this latitude.

What is a normal vitamin D level?+

NIH considers below 12 ng/mL deficient and 12 to 20 ng/mL low. Most clinicians consider 20 to 50 ng/mL a healthy range.

Is D3 better than D2?+

Studies show D3 raises blood levels a little more effectively. Both work. D3 is the usual choice for over-the-counter supplements.

Can I take too much vitamin D?+

Yes. Staying under 4,000 IU per day is the general safe limit for adults unless a clinician prescribes more for a short time.

Does vitamin D prevent colds or cancer?+

Large trials like VITAL did not find that vitamin D prevents cancer or heart disease in people who were not deficient. Evidence for colds is mixed and weak.

Sources: NIH Office of Dietary Supplements, Vitamin D Fact Sheet for Health Professionals; VITAL trial (Manson et al., NEJM 2019; LeBoff et al., NEJM 2022); Endocrine Society 2024 vitamin D guideline.

All treatments are medical services. Every guest is screened, and every treatment is prescribed by a licensed provider. Nothing on this page is medical advice for you personally, and the opinions summarized here belong to the doctors named, not to Zen IV Spa. Talk to a provider before starting or stopping anything.