Q: During a very cold winter, I began to feel more sad than usual, as well as fuzzy, forgetful and achy. This worried me enough to send me to the doctor.

All my blood tests were fine except for my vitamin D, which was very low. Some high-dose supplements eventually caught me up, but apparently my ordinary multivitamin hadn’t been working.

Now I am reading that low vitamin D has been linked to breast cancer, immune problems and other conditions, as well as seasonal affective disorder. If I couldn’t get enough sun exposure to make vitamin D where I live, below the Mason-Dixon line, what about people in the North? Can older people who don’t go outside get enough vitamin D?

A: Research links low circulating levels of vitamin D to seasonal affective disorder (SAD) and depression (Psychiatry Research, May 30, 2015; PLoS One, Sept. 23, 2015).

Vitamin D deficiency also has been associated with conditions such as cancer, high blood pressure, arthritis, osteoporosis, diabetes and multiple sclerosis (Nutrition Journal, Dec. 8, 2010).

You are correct that people in Northern states may have difficulty getting enough vitamin D. In fact, the National Health and Nutrition Examination Survey showed that 29 percent of Americans were deficient in vitamin D and another 41 percent had low levels (British Journal of Nutrition, April 28, 2018).

You can learn more about optimal vitamin D levels and supplements in our “Guide to Vitamin D Deficiency.” Anyone who would like a copy, please send $3 in check or money order with a long (No. 10), stamped (71 cents), self-addressed envelope to: Graedons’ People’s Pharmacy, No. D-23, P.O. Box 52027, Durham, NC 27717-2027. It also can be downloaded for $2 from our website: www.peoplespharmacy.com.

Q: Some years ago, I saw a hand surgeon for a painful thumb. She injected it with cortisone and then it locked up, so she wanted to operate.

Then I read in your column that Boniva can cause intractable joint pain. Low and behold, I was taking Boniva!

I stopped the drug, and soon the pain stopped, too. No more meds for osteopenia. I am embarrassed to tell you that I am a pharmacist, still working after 59 years.

A: Thank you for sharing your experience. Others also have reported joint, muscle and back pain while taking ibandronate (Boniva).

Q: I am an asthmatic. When I was a child and young adult, terpin hydrate was the only cough medicine that could calm my coughing spells. Terpin hydrate saved my life more than once!

Over-the-counter cough meds simply do not work for me. I now have a severe cough, and several brands of cough relief meds have been completely ineffective.

I’ve been looking for terpin hydrate, but my pharmacy does not carry it. Could you please advise?

A: Terpin hydrate was a popular cough medicine from the 1880s till the 1990s. This expectorant was created from ingredients in thyme, oregano and eucalyptus. It also was manufactured from the resin of pine trees (oil of turpentine).

In the 1990s, the Food and Drug Administration determined that there was not enough evidence of effectiveness, and the compound was effectively banned. Many other readers have asked how to locate this old-fashioned remedy.

You can still obtain terpin hydrate from a compounding pharmacy. To locate one in your area, search www.IACPRX.org. You will need a prescription from your physician, however.