Nurse-Led Strategies for Vitamin D in Cancer Care

In oncology, supportive care requires a cohesive, interdisciplinary approach where nursing staff serve as the frontline defense against treatment-related complications. Oncology nurses are a clinical lifeline for patients, uniquely positioned to recognize treatment-induced side effects—such as diarrhea, mucositis, and rapid weight loss—that compromise nutritional status and treatment tolerance.

Crucial to this supportive regimen is the optimization of vitamin D, a fat-soluble pre-hormone that regulates immune function, skeletal bone health, and post-treatment recovery. However, systemic barriers, including patient misconceptions regarding restrictive dieting and insurance limitations on laboratory testing—which can require nurse advocacy through ICD-10 diagnostic coding—frequently delay necessary clinical nutrition interventions.

In this Q&A, Jeanna Brouwer, RDN, an outpatient oncology dietitian at the OSF HealthCare Cancer Institute, discusses how oncology nurses can dismantle patient myths, secure early dietitian referrals, and collaborate to manage complex clinical scenarios. Brouwer outlines actionable nursing strategies to optimize supportive care and enhance patient survivorship, ranging from baseline vitamin D screening in gastrointestinal resections to navigating highly tailored supplementation—such as sublingual liposomal drops for pancreatic insufficiency, spacing out calcium and iron to avoid drug-nutrient interactions, and recommending third-party tested (USP/NSF) brands.

Recent literature has highlighted how altered GI anatomy severely disrupts fat-soluble vitamin absorption in outpatient oncology settings. What baseline clinical cues or screening protocols should oncology nurses be using to catch subtle vitamin D deficiencies early, especially in patients with GI cancers or treatment-induced mucosal damage?

I like to encourage my nurses that if we know the patient is going to meet with a surgeon for a potential GI oncologic resection or surgical procedure, that we should order vitamin D on top of the necessary lab panels that we're going to start with, and get a baseline, and that'll help catch any prior deficiency, and then we can work with what we need to do after that surgery and the type of malabsorption that can be happening, and it'll help us dose that vitamin D more appropriately.

Trials have evaluated high-dose vitamin D3 alongside standard chemo regimens. When a patient is prescribed high-dose protocols, what specific monitoring parameters or signs of toxicity or hypercalcemia should nurses track? And how do you help nurses counsel patients on the difference between over-the-counter maintenance doses and high-dose therapeutic regimen?

Unfortunately, in an outpatient setting, we can be limited to lab coverage for vitamin D. Your typical private pay insurance will only cover a vitamin D once a year if you are falling within their normal range. So sometimes having that conversation with patients or learning how to properly use different diagnosis codes, different ICD-10 codes, recommending that to the doctor, like malabsorption or exocrine pancreatic insufficiency, to get that lab order covered, I think that's important for the nurses to advocate for the patients, so we can get multiple vitamin D (checks) within a year's time.

Just going to your local Costco or Walmart may not give you the most sufficient vitamin D, and really helping them walk through what dose on the bottle that we're looking for, the form that it's coming in, and when and how to properly take that vitamin D are all excellent things that nurses can help advocate for. For example, if it's the non-liposomal form, then you want to make sure you're taking it with a meal to help that fat, if the patient needs pancreatic enzymes, wanting to encourage that they're using that to help their fat be absorbed, thus helping that vitamin D be absorbed, and then you know if their vitamin D lab is inching up towards the 100 region, monitoring their calcium too, making sure that we're getting lab orders on that, and knowing that that can be a side effect if we're going pretty high into the extremes when our labs are popping up.

Large-scale studies suggest a potential reduction in metastatic or fatal cancer risk associated with vitamin D supplementation. Patients frequently read these headlines and bring questions into their infusion nurses. How do you recommend nurses contextualize findings like these without creating false expectations or encouraging unmonitored mega-dosing?

I think a good starting point is recognizing that anywhere from 80% to 90% of Americans are walking around deficient. Obviously, depending on where we live, that can vary. But letting them know that vitamin D is important in general for our health, longevity as we age, and so if they are deficient, it is good to get them in a more healthier range. But also letting them know vitamin D is responsible for a ton of things in our body, so it definitely can help protect our body long-term. We're not quite sure the exact mechanisms of what that is doing in a protective survivorship role, but letting them know it's definitely good about it being a part of our general health protection plan as a cancer patient going through treatment or walking into survivorship, but not to rely on it as a quick fix and solely the thing that's going to prevent any reoccurrence.

Review papers on fat-soluble vitamins emphasize the complex balance between vitamins A, D, E, and K, where excessive intake of one can sometimes interfere with the absorption or metabolism of another. Are there common drug-nutrient or nutrient-nutrient interactions that oncology nurses should be particularly vigilant about when reviewing a patient's supplement list?

One of the most common ones is iron and calcium. When we're taking our vitamins, it can become very nitpicky and cumbersome to the patient. And so, if you're seeing them on a whole host, they have vitamin D plus a calcium, and they're taking iron and vitamin C and a separate calcium, or they've had bariatric surgery and they're on a large-dose calcium supplement, making sure that we space out calcium and iron, looking at meal timing, if food is prevalent in the stomach, also asking, do they know what type of form it is? Can they show a picture of what supplement they're taking? That can also help play a role in that absorption purpose.

Oncology nurses are often the first line in identifying treatment side effects like diarrhea, mucositis, or rapid weight loss that can directly impair nutrient absorption. How can outpatient nurses best collaborate with oncology dietitians to establish timely referral triggers and maintain coordinated care plans for patients who are at high risk for micronutrient depletion?

My nurses are probably my lifeline to my patient. Obviously, getting that nurse the education that we can provide as dietitians. I think a lot of times, if a nurse brings up, "Oh my gosh, you're having mucositis, you're having diarrhea. How about we get you set up with a dietitian?” The patient often thinks, "Oh, they're going to tell me what I can and cannot eat, or just want me to eat healthier or lose weight,” and letting that patient know from a nurse's perspective, no, they're going to help manage these side effects, get you nourished, feeling stronger, and it's not going to be anything that you may commonly think of when you hear the word dietitian. They're going to really help you fight and survive throughout this cancer treatment and make these side effects diminished as possible. That's the first and foremost. And getting those referrals right over to the dietitian, reaching out and saying, "Hey, they're really struggling. Can we get them in soon?” And advocating for sooner appointments is always something that I love when my nurses reach out to me for.

Reference

1. OSF HealthCare. Why vitamin D matters during cancer treatment. OSF HealthCare Newsroom. Published July 29, 2026. Accessed August 19, 2026. https://newsroom.osfhealthcare.org/why-vitamin-d-matters-during-cancer-treatment/