Do you need that vitamin? Review this checklist first

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Before buying vitamin supplements, consider whether you have deficiency symptoms, whether a diet change can solve the issue and whether your doctor recommends them. (Shutterstock)

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Before buying vitamin supplements, consider whether a doctor has recommended them, whether you have symptoms of deficiency or whether a diet change can solve the issue.

Different vitamins behave differently: Fat-soluble vitamins can be stored in the body; water-soluble vitamins can’t, and your body eliminates any extra nutrients via urine.

Taking a higher dose than is recommended isn’t always better for you. Too many fat-soluble vitamins can cause toxicity, and taking too many water-soluble vitamins may be a waste of money.

Do you need to take vitamin (fill in the blank)? One walk down a grocery store’s supplement aisle may have you believing you are deficient in everything. Good news: That’s highly unlikely.

Here’s a step-by-step guide to deciding whether the gummies or pills are worth your money.

Your body needs 13 essential vitamins to function. They have alphabet letter names, but some have alternate names. Vitamin B2 is the same as riboflavin, for example.

Essential vitamins are different from essential minerals  such as iron, calcium, magnesium, and phosphorus. Over-the-counter supplements typically include both kinds of micronutrients, but the way they function in your body is not the same.

This guide focuses on vitamins. But many of the tips — talking to your doctor, reviewing your diets, and closely reading labels — apply to minerals as well.

Step 1: Do you have blood work that shows you are deficient in a vitamin? Or has a doctor told you to take a supplement?

Routine physical blood tests usually don't check for all vitamin deficiencies. Your doctor may suspect you have certain vitamin deficiencies based on your diet, symptoms, risk factors, or what your physical exam reveals. The most common tests doctors order are for vitamin D, vitamin B12, and vitamin B9 (folate/folic acid), because they are some of the most common deficiencies in the U.S.

"We don’t test blindly; we test based on clinical suspicion," said Dr. Alex McDonald, a family medicine doctor at Kaiser Permanente. "A physician might order thiamine (B1) in a patient with alcohol use disorder, vitamin A in someone with fat malabsorption or chronic inflammatory bowel disease, or vitamin C in someone with poor diet and wound healing problems."

It is possible to test your levels for all 13 different vitamins, but testing for everything isn’t necessarily the best approach, McDonald said. A test might flag that your levels are high or low in a particular vitamin without giving clear information about whether it’s of clinical significance. That could create more anxiety than what is merited.

"Every lab result needs to be interpreted in context, because ‘normal’ can look different depending on the person and their situation," said Dr. Michael Richardson, a family medicine doctor in Wellesley, Massachusetts.

If your blood work shows you are low in a vitamin or mineral, talk to your doctor about whether it's best resolved through diet or with a supplement. A physician can guide you through the best dose and how long you should take it.

Step 2: Do you have any symptoms?

Some vitamin deficiency symptoms are very specific — lack of vitamin A causes night blindness, for example. Others are more general like fatigue, or muscle weakness and can be a sign of multiple different deficiencies, including vitamin D and vitamin B12.

Most vitamin deficiencies are rare in the U.S., but certain factors can put you at greater risk for deficiency: keeping a vegetarian or vegan diet, having limited food intake, celiac disease, Crohn’s disease, chronic alcohol use, or other conditions that affect how the body absorbs nutrients.

Here’s a table of the 13 vitamins and their associated deficiency symptoms.

Don’t fret if something sounds familiar. Just because you have a symptom doesn’t mean vitamin deficiency is the cause, especially if it is a very general symptom like fatigue. But it could be a clue to follow up with your doctor.

Step 3: What vitamins are you getting (or forgetting) from your diet?

Before reaching for a pricey over-the-counter supplement, look up foods that are high in the vitamin you seek.

"It is always better to get your vitamins and minerals through whole food sources, particularly plants and lots of colors on your plate," McDonald said. "However, supplements can be a good insurance plan when your diet is not perfect."

If you are on a diet that restricts what foods you eat — vegetarian, vegan, paleo, for example — check to see if those diets are associated with any particular deficiencies.

Vegans, for example, can struggle to get sufficient B12 through their diets because i…