Boost Your Immune System: Carewell's Best Vitamins and Supplements to Take When Sick

Chad Birt

Written by Chad Birt on Tue Jan 09 2024.

Assorted pills and capsules.

Cold and flu season is here. You might not be able to avoid getting sick, but you can take steps to boost your immune system. Plus, it never hurts to stock your medicine cabinet so you have essential supplies if you or your care recipient get sick. 

Here, we explain why you’re more likely to get sick during the winter, highlight 8 of our best immune-boosting vitamins and supplements, and answer some of the most common cold and flu-related questions our Care Team receives.

Why Are Viruses, Like The Cold and Flu, More Common In Winter?

Viral illnesses can occur at any time of year, but they’re more common during the winter for two reasons. 

First, when the weather is cold outside, we spend more time indoors. Since respiratory viruses like the cold and flu cause infection through close, face-to-face contact, it’s no wonder they spread more easily during the cooler months.

Second, cooler temperatures cause the air to dry out, and dry air makes it easier for viruses to spread. That’s because virus particles survive twice as long in dry air, increasing the risk of infection.

Can Vitamins and Supplements Help Boost My Immune System?

Most healthy people get their vitamins, minerals, and nutrients from the foods they eat, but even if you focus on balanced nutrition, you may develop a deficiency. In fact, it’s estimated that up to 31% of Americans have at least one nutrient deficiency. The risk is even greater in older adults, especially for those who have difficulty chewing and swallowing.

When used under a doctor’s supervision, vitamins, and nutritional supplements can restore nutrient levels to balance and provide immune-boosting properties

Carewell’s Best Vitamins and Supplements to Take When Sick

We frequently hear from family caregivers who need help choosing vitamins and supplements. The need is even greater this time of year when the risk of upper respiratory viruses is more prevalent. To make your search easier, we’ve curated a shoppable list of some of our favorite vitamins and supplements. Those featured are a mix of our top-rated and best-selling products. Whenever possible, we’ve included real customer feedback under the heading “Hear It From a User/Caregiver.” 

1) Nordic Naturals ProOmega-D, soft gels

Vitamin D plays a vital role in various immune responses, but up to 42% of adults are vitamin D deficient. If you’re worried about your or your loved one’s risk, add this Nordic Naturals vitamin D supplement to your medicine cabinet. Each soft gel capsule contains 1,000 international units (IU), which is in line with the National Institute of Health’s daily vitamin D intake recommendations.

Key Benefits & Features

  • Contains added vitamin D3

  • Provides high-intensity Omega-3 support for overall cellular functioning

  • Helps regulate the absorption of calcium and phosphorous

2) Nordic Naturals ProOmega 2000 soft gels, lemon flavor

This omega-3 supplement contains 2,000 milligrams of the omega-3 fatty acids, EPA and DHA, both of which are key to healthy immune function. Taking just two soft gels per day can help maximize your omega-3 intake and provide support for you or your loved one’s immune system, brain, eyes, and joints.

Key Benefits & Features

  • Lemon flavor

  • Promotes healthy cellular signaling and metabolic pathways

  • Highest-concentration formula available

Hear it from a caregiver

“[I’ve] used this product before [as it was] doctor recommended.”

- James J. 

3) Nature’s Bounty Super Potency Biotin, 5,000 mg

Biotin, or vitamin H, is a member of the B complex vitamin group. It’s typically associated with improved hair, skin, and nail health, but research suggests it may bolster the immune system, too. One study, published in the American Journal of Physiology-Cell Physiology, found that people who were biotin deficient were also more likely to experience chronic inflammation –– a key marker of disease. 

Nature’s Bounty super potency biotin provides countless benefits, including healthier, thicker hair, vibrant skin, and enhanced immunity. 

Key Benefits & Features

  • Helps support healthy skin, hair, and nails

  • May increase natural immunity by reducing inflammation

  • Provides ample amounts of the essential nutrient for optimal results

4) Nutricia UTI-Stat Cranberry Oral Supplement

Urinary tract infections (UTIs) affect people of all ages, but they’re especially common in older adults. Studies show that up to 30% of women 85 and older get at least one UTI a year and the results are similar for men. When incontinence is added to the mix, the risk is even greater. Consider that one-third of infections in nursing homes are UTI-related.

Supporting your loved one’s immune system may help prevent the incidence of UTIs. Nutricia’s cranberry oral supplement contains several immune boosters, including vitamin C. It’s all-natural and provides prompt relief.

Key Benefits & Features

  • Stimulates the growth of bifidobacteria (microorganisms that support gut health and fight off harmful bacteria)

  • Contains vitamin C to support immune health

  • Contains bromelain, an immune-boosting enzyme found in pineapple

Hear it from a caregiver

“UTI Stat arrived quickly. Very pleased with the product!”

- Sharon T. 

Nutricia UTI-Stat Cranberry Oral Supplement, 78387, 30 oz. Bottle - 1 Each
Nutricia UTI-Stat Cranberry Oral Supplement

Price: $10.66 - $170.99

5) Nature’s Bounty High Potency D3, 1000, IU

Vitamin D3 is often called the “sunshine vitamin,” because when the sun’s ultraviolet rays come in contact with the skin, vitamin D3 is synthesized. Vitamin D3 contributes to various bodily processes, including metabolism and mood, but it’s also been linked to improved immunity. 

Many people take vitamin D3 during the winter months when there’s less sunlight, but it may be just as beneficial the rest of the year. That’s because one study published in the peer-reviewed journal BMJ found that vitamin D3 supplementation reduced the risk of cancer death by up to 15%.

Key Benefits & Features

  • Contains the maximum amount of vitamin D3 for optimal results

  • May help boost immunity

  • May help alleviate depression and seasonal affective disorder (SAD)

6) Nature’s Bounty, Quick Dissolve Vitamin B-12

Many people associate Vitamin B-12 with increased energy and improved nerve function, but the supplement can also support your immune system during cold and flu season. More specifically, it helps protect the body from viral infections. 

Indeed, scientists have confirmed these benefits. A study published in the Oxford University Press concluded that people with adequate vitamin B-12 levels were less likely to experience severe outcomes from viral illnesses, like COVID-19

Key Benefits & Features

  • Helps keep nerve and blood cells healthy

  • May boost immunity

  • Helps convert the food you eat into energy

Hear it from a caregiver

“I love, love, love [these] sublingual vitamins. [The] easiest way to take, rather than swallowing pills.”

- Marylou C.

Image Not Available

7) Nature’s Bounty Acidophilus Probiotic

This Nature’s Bounty probiotic contains acidophilus, a species of “good” bacteria naturally found in the human digestive tract. Acidophilus breaks down food and helps your body absorb nutrients, but certain health problems can significantly impact the amount of good bacteria in your gut and throw your body out of balance.

This oral supplement provides an easy, effective way to restore your acidophilus levels to balance. Doing so can improve your digestive health and immunity and even address food sensitivities, like lactose intolerance.

Key Benefits & Features

  • Increases the amount of friendly bacteria in the gut

  • The supplement contains more than 100 million active microorganisms

  • Gluten-free, dairy-free, and wheat-free

Hear it from a caregiver

“Good value!”

- Laura N.

8) Nature’s Bounty Calcium & Vitamin D3

Our customers often take this calcium and vitamin D3 supplement to support bone health. However, the included nutrients (vitamin D3 and calcium) support immunity and immune system function as well. Calcium, in particular, helps T-cells (the cells that fight off harmful invaders) multiply and defend against viruses and bacteria.

Key Benefits & Features

  • Enhanced with vitamin D to assist with calcium absorption

  • Supports immune health

  • 1,200 mg calcium + 25 mcg (1,000 ICU) per capsule

Hear it from a caregiver

“Much more convenient and easier to take. 1,200 mg in 2 capsules rather than 4 capsules.”

- Joann E.

Nature's Bounty Calcium & Vitamin D3
Nature's Bounty Calcium & Vitamin D3

Price: $19.61

Get Fast, Free Vitamin and Supplement Shipping with Autoship

If you or your loved one are sick (or at greater risk of getting sick) you need to have certain supplies on-hand. We understand, which is why we offer fast, free shipping on orders $49+. Signing up for Autoship is an easy way to receive vitamins and supplements regularly. Some products even qualify for an additional 5% off.

We Can Help You Choose Immune-Boosting Vitamins and Supplements!

Choosing the right vitamins and nutritional supplements for yourself or a loved one can be challenging. We encourage you to reach out if you have questions or need product recommendations. Our friendly Care Team is available 24/7 and here to help! Call (800) 696-CARE or send an email to

Best Immune System Supplements - Commonly Asked Questions

1) Does vitamin C help with the flu?

Vitamin C supplementation won’t cure the flu, but it can support your immune system and help speed up your body’s healing process. One study found that vitamin C supplementation reduced the duration of a cold (another common respiratory virus) by up to 8%. The severity of cold symptoms, like congestion and sore throat, was also reduced.

2) How can I boost my immune system?

The easiest way to boost your immune system is to live a healthy, active lifestyle. You can’t prevent infections altogether, but several steps can reduce your risk. Generally speaking, experts recommend eating a nutritious diet, exercising regularly, getting plenty of sleep, and keeping your stress levels in check.

3) How can I prevent a cold?

The easiest way to prevent a cold is to avoid being around others who are sick. Since that’s not always possible, practice good hand hygiene, consider wearing a mask in crowded places, and avoid touching certain surfaces in public, like door knobs and handrails. Likewise, get your annual flu shot and stay home if you feel sick.

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Chad Birt
Chad Birt

Chad Birt is a freelance medical writer who resides in Astoria, Oregon. When he isn't behind a keyboard, you can find him hiking, camping, or birdwatching with his wife Ella and their two dogs, Diane and Thoreau.