What Vitamin Deficiency Causes Dry Eyes?

Vitamin A deficiency is the best-established nutritional cause of dry eyes, a connection recognized in medicine for thousands of years. But research over the past decade has made the picture more complex: low vitamin D is now consistently linked to dry eye disease, and vitamin B12 deficiency can produce eye pain and dryness symptoms that resist standard treatment. Which deficiency matters most for you depends on where you live, what you eat, and whether your body absorbs nutrients normally.

Vitamin A and the Tear Film

Vitamin A has the longest and most direct relationship with eye dryness of any nutrient. When levels drop low enough, the condition is called xerophthalmia, a term that literally means “dry eye” in Greek. The surface of the eye depends on vitamin A to produce mucin, a slippery protein that helps the tear film spread evenly and stick to the cornea rather than sliding off. Without enough vitamin A, tears become unstable, the conjunctiva dries out, and in severe cases the cornea itself can break down and scar.¹

In a short-term supplementation study, participants with dry eye disease who took oral vitamin A showed improved tear stability, better mucin production, and less ocular discomfort.² One comparison trial found that oral vitamin A supplements lasted longer and worked better than commercially available lubricant eye drops for managing dryness.³ That finding is worth knowing if you have been reaching for artificial tears without considering whether a dietary gap might be part of the problem.

Severe vitamin A deficiency is uncommon in wealthy countries today, but it remains a significant global health issue. Vision loss linked to vitamin A deficiency was the eighth most common cause of impaired vision worldwide as of 2017, and the burden grew by roughly 9% between 1990 and 2017, concentrated in countries with lower development indices.⁴ Even in high-income countries, xerophthalmia still appears, particularly in people with absorption problems or severely restricted diets.

The Vitamin D Connection

While vitamin A’s role in eye dryness has been understood for centuries, the link between vitamin D and dry eye disease is newer and has grown increasingly convincing. A large population-based study tracked patients with and without vitamin D deficiency and found that about 3.3% of vitamin D-deficient individuals developed dry eye disease, compared with 2.7% of those with normal levels. That translated to roughly a 29% higher risk of developing dry eye in the deficient group.⁵

A systematic review and meta-analysis pooling data across multiple studies confirmed the pattern: people with dry eye had serum vitamin D levels about 4 ng/mL lower on average than healthy controls, produced fewer tears on standardized testing, and reported worse symptoms.⁶ A separate meta-analysis specifically looking at tear breakup time and symptom scores found the same direction of effect, and also noted that people with primary Sjögren’s syndrome, an autoimmune condition that attacks moisture-producing glands, tend to have lower vitamin D levels than the general population.⁷

The mechanism appears to be immunological rather than structural. Vitamin D helps regulate immune cells on the surface of the eye, and animal studies have shown it can suppress inflammation in the cornea and conjunctiva.⁸ When vitamin D is low, this anti-inflammatory brake weakens, and the chronic low-grade inflammation that drives many cases of dry eye can intensify.⁹ A review of supplementation evidence found that in people who are actually deficient, restoring vitamin D levels reduces dry eye symptoms and increases tear volume.¹⁰

This matters practically because vitamin D deficiency is extremely common. In one study of health science students, almost 80% had deficient or insufficient vitamin D levels, and there was a strong negative correlation between those levels and dry eye symptom severity.¹¹ If you spend most of your time indoors, live at a high latitude, or rarely eat fatty fish and fortified dairy, your odds of being low in vitamin D are substantial, and your dry eyes may be partly a downstream consequence.

Vitamin B12 and Neuropathic Eye Pain

Vitamin B12 enters the dry eye picture from a different angle. Rather than directly affecting the tear film, B12 deficiency damages nerves, and the cornea is one of the most densely innervated tissues in the body. When those nerves malfunction, they can produce burning, stinging, and a gritty sensation that looks and feels exactly like severe dry eye, even when tear production is sometimes adequate. This is called neuropathic ocular pain, and it is notoriously hard to treat with standard dry eye therapies like artificial tears or anti-inflammatory drops.

A study evaluating patients with severe dry eye disease and resistant pain found that B12 deficiency was associated with this neuropathic component. The researchers recommended checking serum B12 levels in anyone whose dry eye pain does not respond to conventional treatment.¹² A case report documented a patient whose ocular symptoms, mimicking severe dry eye, resolved with B12 supplementation alone, further supporting B12 as something clinicians should consider in the differential.¹³

B12 deficiency is worth thinking about if you follow a vegan or strict vegetarian diet, are over 60 (stomach acid production drops with age, reducing B12 absorption), take long-term acid-reducing medications, or have conditions affecting the gut like Crohn’s disease. The symptoms overlap so heavily with conventional dry eye that without a blood test, neither you nor your eye doctor would necessarily think to look for it.

Antioxidant Vitamins C and E

Vitamin C is one of the antioxidants naturally present in tear fluid, where it protects the ocular surface against oxidative damage. When researchers have looked at whether supplementing vitamins C and E helps dry eye symptoms, the results suggest a synergistic effect: neither vitamin alone did much to reduce pain, but the combination showed antinociceptive effects, meaning it dampened the nerve-based pain component of dry eye.¹⁴ The evidence here is thinner than for vitamins A and D, and no one would call vitamin C deficiency a primary driver of dry eye disease. But for people with intractable symptoms who are already addressing the major deficiencies, antioxidant support seems to contribute something, particularly on the pain and discomfort side.

How Screen Time Makes Everything Worse

You might notice your eyes feel driest during or after long stretches at a computer or on your phone. Screen use reduces your blink rate, which causes the tear film to evaporate faster. By itself, that is enough to trigger or worsen dry eye symptoms. But the same indoor lifestyle that pins you in front of a screen also limits sun exposure, which is the body’s primary way of producing vitamin D.

The study of health science students mentioned earlier captured this double effect neatly: both low vitamin D and longer screen time independently correlated with worse dry eye symptoms, and screen time alone accounted for about a third of the variance in symptom severity.¹¹ In other words, the modern indoor lifestyle creates a two-pronged attack on your tear film: less vitamin D production and less blinking. Addressing one without the other gives incomplete relief.

The Isotretinoin Paradox

Here is an irony worth knowing: isotretinoin, the powerful acne medication commonly known by its former brand name Accutane, is a synthetic derivative of vitamin A. You might expect a vitamin A-related drug to help eyes. Instead, it is one of the most reliable pharmaceutical causes of dry eye. The reason is that isotretinoin shrinks oil-producing glands throughout the body, including the meibomian glands in the eyelids. These glands secrete the oily outer layer of the tear film that prevents tears from evaporating too quickly. When they shrink and malfunction, the result is evaporative dry eye.

A study tracking patients with acne through isotretinoin treatment found substantial deterioration in meibomian gland structure and lid assessments during the course of therapy. The glands partially recovered after the drug was stopped, but the damage during treatment was significant.¹⁵ Another pilot study confirmed that isotretinoin affected meibomian gland morphology and caused tear film instability consistent with evaporative dryness.¹⁶

If you are taking or considering isotretinoin for acne, this is practical information: being proactive about eye lubrication during treatment can help, and the dryness typically improves after you finish the course. The paradox also illustrates that “more vitamin A is better for eyes” is too simple a story. The form of vitamin A matters enormously, and retinoids at pharmacological doses do something very different to the ocular surface than dietary vitamin A does.

When Malabsorption Is the Real Problem

Sometimes the issue is not what you eat but whether your body can absorb it. Bariatric surgery, particularly procedures that bypass portions of the stomach and small intestine, creates a well-documented risk of vitamin A deficiency. Because vitamin A is fat-soluble and absorbed primarily in the upper small intestine, bypass procedures can dramatically reduce how much gets into the bloodstream even if the diet contains plenty.

Case reports describe patients developing xerophthalmia, night blindness, and even progression toward legal blindness after gastric bypass surgery due to inadequate vitamin A supplementation afterward.¹⁷ A review aimed at ophthalmologists emphasized that bariatric procedures, especially those that physically bypass nutrient-absorption sites, lead to deficiencies that manifest as corneal ulceration, dry conjunctiva, and night vision loss.¹⁸

The same logic applies to other malabsorptive conditions: celiac disease, inflammatory bowel disease, chronic pancreatitis, and cystic fibrosis can all impair absorption of fat-soluble vitamins (A, D, E, and K) as well as B12. If you have any of these conditions and are experiencing dry eyes, a blood panel checking these vitamins is a reasonable step before assuming the problem is purely environmental or age-related.

What Supplementation Can and Cannot Do

A review of vitamin supplementation studies for ocular surface disease found that in patients who are genuinely deficient, the benefits are fairly clear: systemic vitamin A reduces both the signs and symptoms of dry eye, and systemic vitamin D supplementation reduces symptoms and increases tear volume.¹⁰ Topical vitamin A (in the form of eye drops or ointments) also showed benefit for dry eye signs and symptoms in the studies reviewed.

The critical qualifier there is “in patients who are genuinely deficient.” If your vitamin levels are already normal, supplementation is unlikely to help your dry eyes and, in the case of vitamin A, can be harmful at high doses. Vitamin A toxicity causes headaches, nausea, liver damage, and ironically can worsen skin and eye problems. The threshold for toxicity is not especially high relative to the recommended daily intake, which is why vitamin A supplementation should be guided by a blood test confirming deficiency rather than guesswork.

For vitamin D, the risk of supplementation at moderate doses is lower, but the same principle applies: it helps if you are actually low. Given how common vitamin D insufficiency is, many people with unexplained dry eyes may benefit from a simple blood test. If you are below the normal range, correcting the deficiency is inexpensive and may address not just your eyes but other inflammation-related issues.

Ancient Liver Juice and the Oldest Nutritional Disease

The connection between diet and eye health is one of the oldest observations in recorded medicine. Ancient Egyptians described night blindness as early as 1500 BC in the Ebers Papyrus, and the remedy they recorded was striking: squeezing juice from animal liver and instilling it directly onto the eye’s surface.¹⁹ The Egyptians had no concept of vitamins, but liver is one of the richest dietary sources of vitamin A, so the treatment worked. Babylonian, Greek, and Arab physicians independently arrived at the same remedy over the following millennia.²⁰

Night blindness is sometimes called the first clearly recognized nutritional deficiency disease. The reason it was identified so early is that the symptom is unmistakable and the dietary cure is fast-acting. Dry eyes from vitamin A deficiency follow the same underlying biology, just at a less advanced stage. In that sense, if you experience persistent, unexplained eye dryness, you are bumping up against a medical problem that humans have been diagnosing and treating, even without understanding why, for more than four thousand years.