Question 1

What vitamin D level is too low?

Accepted Answer

Below 12 ng/mL (30 nmol/L) is generally considered deficient. Between 12 and 20 ng/mL (30 to 50 nmol/L) is low for some people. Many labs flag anything below 20 or 30 ng/mL, so ask your clinician which target applies to you.

Question 2

Can low vitamin D make you tired?

Accepted Answer

Low vitamin D can cause bone pain and muscle weakness, and some people with deficiency feel tired. Tiredness has many causes, though, and trials have not shown that vitamin D improves energy in people whose levels are already adequate.

Question 3

How long does it take to raise vitamin D?

Accepted Answer

With a regular supplement, blood levels usually rise over several weeks and level off after about two to three months. Clinicians often recheck after about three months if the first result was low.

Question 4

Should I take vitamin D without a test?

Accepted Answer

Many health bodies suggest a modest daily supplement, often 400 to 1,000 IU (10 to 25 micrograms), for groups at higher risk or during winter. Higher doses should be guided by a test and your clinician, because too much vitamin D can be harmful.