5 supplements you should be taking—and when

By Naveed Saleh, MD, MS
Published November 29, 2023

Key Takeaways

  • With so many supplements on the market today, it's good to get back to basics and focus on the most beneficial vitamins and minerals to add to your diet, such as vitamin C and fish oil.

  • Some supplements, such as magnesium, can help with sleep; others, such as vitamin B6, can improve energy levels.

  • Advising your patients to take certain supplements at certain times of day is one effective way to address nutrient deficiency.

Essential nutrients should be regularly consumed by means of a healthy, balanced diet for optimal well-being. But, we don’t always follow the best diets or eat the best foods, which can lead to deficiencies in key vitamins and minerals. That’s where supplements come in.

To enrich and fortify

Nutritional supplement pills—such as those for vitamins, minerals, essential fatty acids, antioxidants, and phytochemicals—can enrich and fortify the body in key areas where diet-based nutrients are lacking. Over-the-counter supplement labels will generally advise how often supplements should be taken and whether they should be taken with meals, because they shouldn't be taken at random.

For some supplements, optimal absorption can depend on the time of day they are taken. Here are five of the most common supplements and the best times of day to take them.


Magnesium is required by every cell and organ in the body for fluid operation, but it is especially important for proper nerve, muscle, and enzyme function. In fact, it’s the fourth most abundant mineral in the body, with about 50% of the body’s magnesium levels found in bone.

As you can imagine, magnesium deficiency can lead to a myriad of health problems, including arrhythmias, diabetes, hypertension, migraines, osteoporosis, premature ejaculation, and premenstrual syndrome.[] Another big health issue? Insomnia. That’s why a good time to take magnesium supplements is bedtime.

Magnesium helps the body and brain relax by triggering the system responsible for calm and relaxation: the parasympathetic nervous system. In one randomized, controlled trial of the association of stress reduction and magnesium intake, 400-mg magnesium supplementation yielded improved parasympathetic and sympathetic tone, which prevented irritability, restlessness, lack of concentration, sleep disorders, and depression.[]

According to the study authors, magnesium supplementation also boosted vagal nerve activity, as well as adaptive/regenerative potential.

Vitamin C

Vitamin C is a powerhouse antioxidant needed for essential body functions, including collagen synthesis, neurotransmitter synthesis, and protein metabolism. It’s key for immune health and has been shown to boost internal and external healing.

Because vitamin C is water-soluble, it can’t be stored in the human body, which means that people need to get adequate intake from food sources and/or supplements. When to take vitamin C supplements, though, can be a little tricky.

Water-soluble vitamins are best absorbed on an empty stomach. But, because vitamin C is highly acidic (another name for vitamin C is L-ascorbic acid), some health experts recommend taking these supplements either right before a meal, with a meal, or directly after a meal to counteract nausea.

Another option is to split up doses to maximize absorption and reduce the risk of nausea. Another tip: As vitamin C must be sourced externally, try taking supplements at the same time every day so that you don’t miss a dose. 

B vitamins

Eight B vitamins make up the B complexes, which are essential for heart and brain health: thiamine (vitamin B1), riboflavin (vitamin B2), niacin (vitamin B3), pantothenic acid (vitamin B5), vitamin B6, biotin (vitamin B7), folic acid (folate), and vitamin B12. B-complex vitamins help the body render energy from consumed foods and facilitate the formation of red blood cells. They are also wonderful for providing stress relief

On the other hand, taking these supplements at bedtime may interfere with sleep. In one trial, Australian researchers found that vitamin B6 taken before bed for 5 days lowered sleep quality and increased morning fatigue.[]

Fish oil

The omega-3 fatty acids found in fish oils have been linked to a wide range of cardiovascular, neurocognitive, ophthalmic, and metabolic health benefits.

Many US adults are not meeting the recommended levels for omega-3 fatty acid intake. Because the body cannot make omega-3 fatty acids on its own, it must be obtained from food—notably, seafood. Fatty fish like salmon and sardines are some of the most potent dietary sources of these substances. But, for those who aren’t the biggest fans of fish, this can be a problem. Luckily, fish oil supplements are a good alternative. 

Although fish oil supplements can be taken at any time, research shows that they are better absorbed during meals.[] Good sources of fat can increase the bioavailability of omega-3 fatty acids, boosting their efficacy. But, for those with a history of acid reflux or indigestion, it’s generally recommended to take fish oil immediately before a meal.[] 


Iron is essential for good health—with insufficient iron levels, you may feel weak, fatigued, or confused. People deficient in iron may also experience shortness of breath, pica and pagophagia, tachycardia, hypothermia, and an increased risk of infection.[]

Taking an oral iron supplement is the most cost-effective way to replenish iron stores. These supplements are available as ferrous sulfate (20% elemental iron), ferrous gluconate (12% elemental iron), and ferrous fumarate (33% elemental iron).

Iron supplements should be taken 30 minutes to 2 hours before meals to ensure full absorption. If upset stomach occurs, however, it can be taken with small amounts of food. Of note, milk, caffeine, antacids, and calcium supplements can decrease iron absorption and, therefore, should not be taken at the same time as iron supplements. On the other hand, vitamin C boosts iron absorption, so it’s a good idea to drink a glass of orange juice before taking these supplements.

What this means for you

Supplements can be a great way to complement or improve your dietary nutritional intake. But, keep in mind that they can’t replicate all the benefits of whole foods. Supplements, therefore, shouldn’t serve as substitutes for whole foods, and should only be taken by those who are nutrient deficient. 

Read Next: These popular supplements are potential health hazards
Share with emailShare to FacebookShare to LinkedInShare to Twitter