Do you need that vitamin? Review this checklist first

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 it is mostly found in animal products. Elimination of dairy products, like in the paleo diet, can make it harder to get enough vitamin D. But in both those cases, there are alternatives that have been fortified with these vitamins and fit into these diets like vitamin D-fortified orange juice, or vitamin B12-fortified cereals.

You might not have to change anything about your diet; you may already be eating the foods you need.

Step 4: Know the difference between water-soluble vitamins and fat-soluble vitamins.

Before you go vitamin-maxxing, it’s important to know the science of how the body stores the nutrients you eat. Knowing which vitamins do what can help you better understand your needs. 

The 13 vitamins can be divided into two groups — fat-soluble and water-soluble — and your body deals with them quite differently.

Fat-soluble vitamins, including vitamins A, D, E and K, can be stored in the body. That means  if you eat extra one day your body can store it for later use. Conversely, if you don’t consume it for a few days your body has a bank to draw on. So if your consumption is inconsistent, it is less of a problem. 

But the ability to accumulate this type of vitamin makes it easier to take too much and risk vitamin toxicity. 

Water-soluble vitamins, including vitamins B and C, aren’t stored in the body for very long. Vitamin B12 is an exception, as it can accumulate in your liver.

Whatever excess water-soluble vitamins your body doesn’t need, it flushes out through urine. This makes it harder to overdo if you take more than recommended.

Because your body is regularly flushing them out, it's more important that these vitamins are a regular part of your diet, rather than occasional. Your body can’t bank the extra, so it’s easier to become deficient quicker. 

Step 5: How much of a vitamin should you take?

If you have determined a supplement is the right choice, it’s important to make sure you’re taking the right dose.

A doctor will have advice. But if you are flying solo, the Food and Nutrition Board of the National Academies of Sciences Engineering, and Medicine provides daily dose recommendations and, in some cases, maximum daily intake guidelines. Experts recommend different doses for males and females based on their hormonal needs and life stages. Generally, for adults they are as follows.

The daily value percentages listed on supplement nutrition labels are designed to communicate safe limits for the general population. Recommendations sometimes vary for people depending on their sex or age.

Still, looking at the daily value percentages on the back of vitamin bottles can give you a sense of how much of your daily needs you are getting from the supplement.

Frequently, bottle labels say the vitamins provide more than 100% the daily need — but more isn’t necessarily better. 

"The body has absorption limits, and the excess can cause harm or just get excreted," McDonald said.

If you take more than the daily recommendation of water-soluble vitamins, your body will flush out the remainder via urine.

Toxicity from water-soluble vitamins is less common, but not impossible. High doses of vitamin B6 have been linked to nerve damage, for example. Best to save your health and money and aim for the recommended dose.

If it’s a fat-soluble vitamin — like vitamins A, D, E or K — your body can store that surplus for later. But that also means it could be risky to take more than the recommended daily dose because they can accumulate in the body and reach toxic levels.

"Vitamin A toxicity, or hypervitaminosis A, can cause liver damage, bone loss, and even birth defects in pregnancy," said McDonald. "Vitamin D toxicity leads to high calcium, which can damage the kidneys."

When calculating how much vitamin you’re taking in daily, don’t forget to factor in how much you get from food sources.