What Vitamin Inadequacies Cause Low Energy? Signs You Shouldn't Ignore

How vitamin inadequacies can lead to low energy

When you're struggling with low energy, pinning down the cause can be difficult. There are many potential factors, but diet often plays a part. While macronutrients like carbohydrates and protein contain the "fuel" for energy production, micronutrients (vitamins and minerals) play a key role as cofactors and signaling molecules to turn that fuel into energy.

And yet, vitamin inadequacies are still possible, even among otherwise healthy people. Fortunately, there are adjustments you can make to start getting your energy back. Let's take a closer look at what vitamin inadequacies cause low energy and how to correct them.

Energy production is like a complex biological relay race. Nutrients from food are broken down, converted into more usable forms, and passed along to the next phase. Eventually, these raw materials reach the mitochondria—cellular power plants—and are turned into ATP, the body's energy currency.

Vitamins and minerals play a crucial role in this process. For example, without sufficient thiamine (B1), mitochondria can't effectively use glucose for fuel.¹ Magnesium binds to and stabilizes ATP and is required for hundreds of reactions that use or generate cellular energy.² Oxygen is also essential for energy production. To reach our cells, oxygen is carried through the bloodstream by hemoglobin in red blood cells, which relies on iron.

When key micronutrients are insufficient, the machinery of energy production may not function optimally, which can contribute to tiredness, 'heavy' or weak limbs, and difficulty focusing.

Why low energy is often linked to vitamin inadequacies

Vitamin inadequacies and low energy are seen even in developed countries. According to the National Health and Nutrition Examination Surveys (NHANES), approximately 96% of people are consuming inadequate amounts of vitamin D, 6% inadequate iron, and 13% vitamin B6.³

Common vitamin inadequacies that affect energy levels

So, what vitamin inadequacy causes low energy? While there isn't any one nutrient shortage that causes tiredness, these are the most important:

B-complex

The eight B vitamins are water-soluble and have to be replenished daily. They work together, meaning an inadequacy in one often impairs the functioning of another. B vitamins are crucial cofactors in ATP production, neurotransmitter synthesis (serotonin, dopamine), red blood cell formation, and maintaining the protective sheath for nerves.⁴ Low levels can lead to difficulty concentrating, mood changes, fatigue, and sleep disturbances.

Vitamin D

We can get vitamin D from sunlight, though it can also be found in fortified foods such as milk, breakfast cereals, orange juice, and yogurt. Vitamin D supports muscle function, immune health, and low levels have been associated with fatigue in some studies.⁵ Emerging research suggests vitamin D may support serotonin regulation, which can influence mood.⁶

Magnesium

As a key enzyme cofactor, magnesium is crucial to every process that uses or transfers ATP. It also helps stabilize ATP. Low magnesium can make minor physical tasks feel difficult.

Iron

Iron is critical for the hemoglobin in red blood cells that carry oxygen through the bloodstream, as well as myoglobin, which stores oxygen in muscles.⁷ It's also the most common nutrient inadequacy worldwide.⁸ This can affect physical stamina and cognition.

For a deeper dive, read our guide to the key vitamins and minerals for energy.

Signs and symptoms of vitamin inadequacy and low energy

When nutrients are limited, tissues with high energy demands—like muscles and the parts of the brain involved in focus—are often the first places people notice symptoms. Signs that you may have insufficient nutrient intake include:

• Feeling out of breath after minor activity (like walking up a flight of stairs)
• Muscle weakness or cramps
• Pale skin
• Tingling in hands or feet
• Dizziness
• Cognitive difficulty
• Mood swings

If you feel you should have more energy than you do, try following these guidelines for boosting energy levels, beginning with a well-rounded diet of whole foods to ensure adequate nutrient intake.

Fatigue can have many causes, and it's important to speak with your doctor if you have concerns about your energy levels.

How to tell if a vitamin inadequacy is affecting your energy

The only way to know for sure if it's a vitamin inadequacy that makes you tired is to see your doctor. They will often recommend lab tests that tell you how much of key nutrients are in your system. You can then work out a plan for addressing shortfalls.

When low energy shouldn't be ignored

Vitamin inadequacies and low energy are often linked, but sluggishness can signal many different health conditions. These symptoms may indicate conditions requiring medical evaluation beyond nutritional support.

Should you take vitamins or supplements for energy?

There's no substitute for a nutrient-rich diet of whole foods. However, when life gets busy, it can be difficult to track nutrient intake consistently.

• Supplements can be a convenient way to fill common nutrient gaps.
• A foundational nutrition supplement, like AG1, can provide numerous key nutrients in a convenient, once-daily drink carefully formulated for enhanced absorption. While supplements can help fill nutrient gaps as part of a proactive wellness routine, they aren't a substitute for medical evaluation of fatigue. If low energy continues, see a doctor first.

How AG1 supports energy levels

If you're proactively looking to support your daily nutrient intake, AG1 delivers more than 75 vitamins, minerals, and whole-food-sourced ingredients—including B-complex and magnesium—that help fill common nutrient gaps.* If you're experiencing signs of low vitamin D levels, such as low energy and achiness, we offer vitamin D as a separate liquid for enhanced absorption. Try AG1 today.

* AG1 doesn't contain significant amounts of iron.

References:

1. Gralak MA, Dębski B, Drywień M. Thiamine deficiency affects glucose transport and β-oxidation in rats. J Anim Physiol Anim Nutr (Berl). 2019;103(5):1629-1635. doi:10.1111/jpn.13146
2. Gröber U, Schmidt J, Kisters K. Magnesium in prevention and therapy. Nutrients. 2015;7(9):8199-8226. doi:10.3390/nu7095388
3. Reider CA, Chung RY, Devarshi PP, Grant RW, Hazels Mitmesser S. Inadequacy of immune health nutrients: intakes in US adults, the 2005-2016 NHANES. Nutrients. 2020;12(6):1735. doi:10.3390/nu12061735
4. Calderón-Ospina CA, Nava-Mesa MO. B vitamins in the nervous system: current knowledge of the biochemical modes of action and synergies of thiamine, pyridoxine, and cobalamin. CNS Neurosci Ther. 2020;26(1):5-13. doi:10.1111/cns.13207
5. Bislev LS, Grove-Laugesen D, Rejnmark L. Vitamin D and muscle health: a systematic review and meta-analysis of randomized placebo-controlled trials. J Bone Miner Res. 2021;36(9):1651-1660. doi:10.1002/jbmr.4412
6. Huiberts LM, Smolders KCHJ. Effects of vitamin D on mood and sleep in the healthy population: interpretations from the serotonergic pathway. Sleep Med Rev. 2021;55:101379. doi:10.1016/j.smrv.2020.101379
7. Obeagu EI. Iron homeostasis and health: understanding its role beyond blood health - a narrative review. Ann Med Surg (Lond). 2025;87(6):3362-3371. doi:10.1097/MS9.0000000000003100
8. Bailey RL, West KP Jr, Black RE. The epidemiology of global micronutrient deficiencies. Ann Nutr Metab. 2015;66 Suppl 2:22-33. doi:10.1159/000371618