Persons taking such a combination supplement (VITMOCOMBO) were not asked which particular vitamins or minerals were included in those supplements, so it is not possible to ascertain whether calcium was included in a given sample person's multi-vitamin/multi-mineral supplement.

In 1987, sample adults were asked, "Did you take any calcium in the past month?"

In 2007, responses to VITMOCALC by sample adults were obtained as follows: While administering the NHIS, interviewers showed respondents a flash card containing a list of vitamins and minerals and asked, "During the past 12 months, have you taken any vitamins or minerals listed on this card for yourself?" Respondents who answered affirmatively (i.e., a "Yes" response in VITYR) were asked, "During the past 30 days, did you take any of these vitamins or minerals?" Sample adults who answered that question affirmatively (i.e., a "Yes" response in VITMO) were instructed, "Please tell me which of these vitamins or minerals you took in the past 30 days. If you take a multi-vitamin or mineral, include it as one supplement." Interviewers were told to "enter all that apply." The questions to collect this information for sample children were similar, except respondents were asked whether the sample child had taken any vitamins or minerals listed on a card.

The 2015 Field Representative's Manual instructed respondents to include any calcium supplements, including Tums or calcium chews. But do not include milk or calcium fortified orange juice and do not include any calcium included in multivitamins.

The other such vitamins/minerals recognized by the NHIS (with years indicating availability) are:

• Calcium (VITMOCALC)

• Coral calcium (VITMOCCALC)

• Chromium (VITMOCHRO)

• Folic acid/folate (VITMOFOLIC)

• Iron (VITMOIRON)

• Magnesium (VITMOMAG)

• Niacin (VITMONIA)

• Vitamin Packet (VITMOPACK)

• Potassium (VITMOPOTA)

• Selenium (VITMOSELN)

• Vitamin A (VITMOVITA)

• Vitamin B6 (VITMOVITB6)

• Vitamin B12 (VITMOVITB12)

• Vitamin B complex (VITMOVITB)

• Vitamin C (VITMOVITC)

• Vitamin D (VITMOVITD)

• Vitamin E (VITMOVITE)

• Vitamin K (VITMOVITK)

• Zinc (VITMOZINC)

• Multivitamin and/or mineral combination (VITMOCOMBO)

For 2007 only, the summary variables VIT1MOST and VIT2MOST report the vitamins and minerals taken most often by sample adults and sample children during the past month. For more information about the full range of variables related to the use of vitamins and minerals, see VITMO.