Supplements for Brain Fog After COVID: An Evidence-Based Overview

Brain fog after COVID is frustrating. You feel slower, struggle to find words, or can’t focus like you used to. Many people experiencing this turn to supplements, hoping for relief. Here’s what research actually shows about which supplements have been studied and what the evidence looks like.

I’m going to be straightforward about what works, what’s uncertain, and what we don’t know yet. Some supplements show promise. Others have little evidence behind them despite being heavily marketed.

What Brain Fog After COVID Actually Looks Like

Brain fog isn’t a medical diagnosis but rather a collection of cognitive symptoms. These include difficulty concentrating, memory problems, trouble finding words, mental fatigue, and feeling like your thoughts are moving through molasses.

After COVID, brain fog can persist for months or even years. Researchers suggest COVID may increase the risk of developing dementia, making cognitive symptoms particularly concerning for people experiencing them long-term.

The underlying mechanisms aren’t fully understood but may involve ongoing inflammation, changes in blood flow to the brain, or persistent effects on neurotransmitter systems.

NAC and Guanfacine: The Most Studied Combination

The most compelling evidence for COVID brain fog comes from Yale researchers who tested NAC combined with guanfacine. They treated 12 patients with persistent cognitive problems after COVID.

Patients took 600 mg of NAC daily along with 1-2 mg of guanfacine. Eight of the 12 patients reported substantial improvements in memory, organizational skills, and multitasking ability. For some, the brain fog completely resolved.

This is significant because it was the first time many of these patients found anything that actually helped. However, the study was small and didn’t include a placebo group, so we can’t be certain how much was due to the supplements versus natural recovery.

NAC is available over the counter. Guanfacine requires a prescription. It’s approved for ADHD and high blood pressure, but doctors can prescribe it off-label for brain fog.

Nicotinamide Riboside: Early Promise for Fatigue and Cognition

A 24-week clinical trial at Massachusetts General Hospital tested nicotinamide riboside, a form of vitamin B3 that boosts NAD+ levels in cells. NAD+ is essential for energy production and may be disrupted by COVID.

The study involved 58 people with long COVID. One group took 2,000 mg of NR daily for 20 weeks. The other started with placebo, then switched to NR after 10 weeks.

Overall group differences were limited, but many participants showed encouraging improvements after taking NR for at least 10 weeks. The researchers noted that boosting NAD+ may offer symptom relief for some individuals, though not everyone responds.

This was a randomized, placebo-controlled trial—a higher quality design than the Yale study. The mixed results suggest NR might help some people but isn’t a universal solution.

Omega-3 Fatty Acids: General Brain Support

Omega-3 fatty acids, particularly DHA and EPA, have been extensively studied for cognitive function. These fats are concentrated in the brain and involved in neurotransmitter function and reducing inflammation.

Multiple studies show omega-3s can improve learning, memory, cognitive well-being, and blood flow in the brain. Research in adults with mild cognitive impairment found that DHA supplementation improved memory and reaction time.

However, there’s limited research specifically on omega-3s for COVID-related brain fog. The general cognitive benefits are well-established, but we can’t assume they translate directly to post-viral symptoms.

Typical doses in studies range from 1-3 grams of combined EPA and DHA daily. Look for supplements with third-party testing verification. Omega-3s can interact with blood thinners.

Magnesium L-Threonate: Brain-Specific Form

Most magnesium supplements don’t cross into the brain very well. Magnesium L-threonate is different—it was specifically developed to increase brain magnesium levels.

Animal studies found that magnesium L-threonate improved memory and learning, even reversing some aspects of brain aging. Rats supplemented with this form showed a 15% improvement in maze navigation and increased synaptic density in brain regions involved in memory.

A human trial in older adults found that supplementation significantly improved cognitive function. Research suggests an optimal serum magnesium concentration of around 0.85 mmol/L for cognitive health—both too low and too high levels increase dementia risk.

No studies have specifically tested magnesium L-threonate for COVID brain fog. But given its demonstrated effects on cognition and the fact that stress depletes magnesium, it’s a reasonable option to consider.

Typical doses are around 2 grams daily, providing about 145 mg of elemental magnesium. This form is more expensive than other magnesium supplements.

Creatine: Beyond Muscle Building

A small German study found that dietary creatine improved post-viral fatigue symptoms, including brain fog, in people with long COVID.

Twelve participants took creatine for three months. By six months, they showed improvements in concentration and mental clarity, along with fatigue, body aches, and breathing issues.

Creatine helps cells produce energy. The brain uses enormous amounts of energy, and energy production problems may contribute to post-viral symptoms.

The study was small and lacked a placebo group. But creatine is well-studied for other uses and has a good safety profile. Standard doses are 3-5 grams daily.

Lithium Aspartate: Mixed Early Results

A University at Buffalo study tested lithium aspartate for long COVID brain fog. This is very different from prescription lithium—the supplement contains 10-15 mg per pill instead of 300-450 mg.

The randomized controlled trial found no benefit from low doses. However, a follow-up dose-finding study with three participants suggested that higher doses of 40-45 mg daily might help.

The lead researcher had initially treated nine of 10 patients with good results before the formal trial. The discrepancy between his clinical observations and the trial results highlights why controlled studies matter.

This supplement needs more research before we can know if it actually works and at what dose. The initial trial was negative, which is important information despite the anecdotal reports.

What About B Vitamins?

You’ll see B vitamins mentioned frequently for brain fog. Some people report taking B-3 (niacinamide) at 500 mg 2-3 times daily with benefits for fatigue and brain fog.

The nicotinamide riboside study above used a form of B3. B vitamins are involved in energy production and NAD+ synthesis, which makes biological sense.

However, anecdotal reports aren’t the same as clinical evidence. B vitamins are water-soluble, so excess is typically excreted. Deficiency can definitely cause cognitive problems, so correcting low levels makes sense.

If you try B vitamins, don’t take very high doses of B6 long-term—nerve damage is possible at extremely high doses. Standard B-complex supplements are generally safe.

Vitamin D: Correct Deficiency First

Severe vitamin D deficiency has been linked to increased dementia risk—potentially doubling it. Vitamin D receptors exist throughout the brain.

Many people with long COVID have low vitamin D levels. Whether supplementation specifically helps brain fog when you’re not deficient is unclear.

Get your vitamin D level checked. If it’s low, supplementing makes sense regardless of whether it helps brain fog. Typical doses are 1,000-2,000 IU daily, though deficiency may require higher amounts temporarily.

What Doesn’t Have Good Evidence

Many supplements are marketed for brain fog without solid research backing. Curcumin (from turmeric) has anti-inflammatory properties and some general brain health research, but no specific studies on COVID brain fog.

Ginkgo biloba, phosphatidylserine, and various proprietary blends often lack rigorous testing. Some may have theoretical benefits, but theory doesn’t equal proof.

Be skeptical of flashy, celebrity-endorsed supplements with heavy branding and limited peer-reviewed studies. Marketing budget doesn’t equal effectiveness.

The Importance of Addressing Root Causes

Supplements might help, but they’re not the whole picture. Brain fog has multiple potential causes: poor sleep, stress, inflammation, nutrient deficiencies, hormonal changes, dehydration.

If you’re not sleeping well, no supplement will fully compensate. If you’re severely stressed or not eating adequately, supplements are addressing symptoms rather than causes.

Consider the basics first. Are you getting 7-9 hours of sleep? Drinking enough water? Eating regular, nutritious meals? Managing stress? Getting some physical activity?

These lifestyle factors have strong evidence behind them for cognitive function and don’t require buying anything.

Realistic Expectations and Trial Periods

No supplement works for everyone. The Yale researchers saw 8 out of 12 patients improve with NAC and guanfacine. That’s a good response rate, but it also means four people didn’t benefit.

If you try a supplement, give it an adequate trial—usually 6-12 weeks. Track specific symptoms rather than relying on general impressions. Are you remembering names better? Finishing tasks more easily? Feeling less mentally exhausted?

Be willing to stop if nothing changes. There’s no point continuing something that isn’t helping you, even if it helped others.

Also be aware of placebo effects. In the lithium study, even people taking placebo reported some improvement. That doesn’t mean the improvements weren’t real to them, but it does mean controlled trials matter.

Safety Considerations You Should Know

Even supplements that are generally safe can cause problems in certain situations.

NAC can interact with nitroglycerin and blood thinners. It can cause nausea in some people.

Omega-3s can increase bleeding risk if you take anticoagulants or have bleeding disorders.

High-dose magnesium can cause diarrhea. People with kidney disease need to be cautious with any magnesium supplement.

Creatine can affect kidney function in people with existing kidney problems.

Guanfacine (if prescribed) can lower blood pressure and cause dry mouth or drowsiness.

Tell your doctor about all supplements you’re taking. Bring the bottles to appointments. Don’t assume that because something is over the counter, it can’t interact with medications or affect health conditions.

Quality Matters with Supplements

Supplements aren’t regulated like medications. Companies can make products of varying quality.

Look for third-party testing from organizations like USP, NSF, or ConsumerLab. This verifies that the supplement contains what it claims and is free from contaminants.

Store supplements properly according to label directions. Some degrade with heat or light exposure.

Be wary of products that make extreme claims or promise to cure conditions. If it sounds too good to be true, it probably is.

The Bottom Line on Supplements for COVID Brain Fog

The best evidence exists for NAC combined with guanfacine, based on the Yale study. It’s small-scale evidence, but the results were meaningful for many patients.

Nicotinamide riboside has some support from a randomized trial, though results were mixed.

Omega-3s and magnesium L-threonate have strong general cognitive research but haven’t been specifically tested for COVID brain fog.

Creatine and lithium aspartate have very preliminary data that needs replication.

Most other supplements lack specific evidence for this condition, even if they have general brain health research.

If you’re struggling with persistent brain fog, discuss options with your doctor. They can check for deficiencies, rule out other causes, and help you decide which supplements might be worth trying based on your specific situation.

Remember that research is ongoing. What we know in 2026 will be different from what we know in 2030. Stay skeptical but also stay open to emerging evidence.