The supplements worth taking at night generally fall into two categories: those that actively improve sleep quality and those that absorb better when paired with an evening meal. Magnesium, melatonin, L-theanine, glycine, and valerian root all have evidence supporting nighttime use for sleep. Casein protein and certain fat-soluble vitamins can also benefit from evening timing, though for different reasons.
Magnesium for Sleep and Relaxation
Magnesium is one of the most well-supported nighttime supplements. It works by enhancing the activity of GABA receptors in the brain, which are your nervous system’s main “calm down” signals. This reduces neuronal excitability and promotes the kind of physical and mental relaxation that helps you fall asleep. It also relaxes muscles through a separate peripheral pathway, which can ease the restlessness or tension that keeps some people awake.
Magnesium glycinate (also called bisglycinate) is the form most commonly recommended for sleep, and for good reason. In a randomized, placebo-controlled trial published in Nature and Science of Sleep, 250 mg of elemental magnesium from bisglycinate improved sleep in healthy adults who reported poor sleep quality. The glycine component may add its own benefit: as an inhibitory neurotransmitter, glycine helps lower core body temperature, which is one of the body’s natural cues for falling asleep.
One important distinction: the NIH sets the upper tolerable intake for supplemental magnesium at 350 mg per day for adults. Going above that threshold increases the risk of diarrhea, nausea, and cramping. If you’re eating magnesium-rich foods throughout the day, a supplement in the 200 to 250 mg range of elemental magnesium is a reasonable evening dose. Check the label carefully, since the total weight of the capsule is much higher than the elemental magnesium it delivers.
Melatonin: Dose and Timing Matter More Than You Think
Melatonin is the most popular sleep supplement, but most people take too much of it too late. The optimal approach, based on circadian rhythm research, is to take it 3 to 4 hours before your desired sleep time. If you want to be asleep by 10 or 11 PM, that means taking it around 6 or 7 PM, not right before you climb into bed. Taking it earlier helps reset your body’s internal clock rather than simply sedating you.
Dose is equally important. Research shows that 0.3 mg to 1 mg best mimics the natural melatonin levels your body produces at night. Most over-the-counter products contain 3 to 10 mg, which is far more than needed. Higher doses lead to higher blood levels for longer periods, which increases the chance of next-day drowsiness and headaches. About 1 in 10 people taking melatonin experience those side effects.
Long-term use deserves some caution. A 2025 American Heart Association scientific statement flagged concerns about chronic melatonin use, noting that data on its long-term cardiovascular safety are lacking. A study found an association between ongoing melatonin supplementation and increased risk of heart failure in people with chronic insomnia, though researchers emphasized this doesn’t prove melatonin caused the problem. In the U.S., melatonin is sold as an unregulated supplement, so quality and potency can vary between brands. Using it for occasional sleep disruptions or jet lag is well supported; relying on it nightly for months or years is less clearly safe.
L-Theanine for Quieting a Busy Mind
L-theanine is an amino acid found naturally in tea leaves. It promotes relaxation without causing drowsiness on its own, which makes it useful if racing thoughts are your main barrier to sleep. A 2019 study found that combining L-theanine with GABA increased both total sleep duration and time spent in REM sleep, the phase most closely tied to feeling mentally restored the next day.
The typical dose ranges from 200 to 500 mg taken in the evening. The Cleveland Clinic recommends not exceeding 500 mg per day and advises against pairing it with caffeine, which would counteract the calming effect. The FDA classifies L-theanine as generally safe, though there are no formal dosing guidelines.
Valerian Root and Ashwagandha
Valerian root has been used as a sleep aid for centuries, and modern research supports doses of 400 to 900 mg of the extract taken up to two hours before bed for insomnia. It’s available as a dry extract in capsule form, typically in the 250 to 600 mg range. Valerian tends to work better with consistent use over a few weeks rather than as an occasional one-off.
Ashwagandha takes a different approach to nighttime support. Rather than acting directly as a sedative, it lowers elevated cortisol levels, your body’s primary stress hormone. If stress or anxiety keeps you wired at night, ashwagandha may help by addressing that underlying hormonal imbalance. Some evidence suggests a specific compound in ashwagandha leaves can induce non-REM sleep, the deep, restorative phase your body uses for physical recovery. It also appears to modulate dopamine activity in the brain during periods of stress.
Casein Protein for Overnight Muscle Recovery
If you exercise regularly, taking 20 to 40 grams of casein protein about 30 minutes before sleep can meaningfully improve your overnight recovery. Casein is a slow-digesting protein that provides a steady supply of amino acids while you sleep. A systematic review found that this dosing window stimulates whole-body protein synthesis during the overnight period in both young and older adults, with possible positive effects on muscle mass and strength when combined with regular resistance training.
Casein works best here because it forms a gel in the stomach, releasing amino acids gradually over several hours. Whey protein digests much faster and doesn’t provide the same sustained effect. Most casein supplements come as a powder you mix into a shake, and the texture is noticeably thicker than whey.
Fat-Soluble Vitamins With Dinner
Fat-soluble vitamins like K2 don’t inherently need to be taken at night, but they do need to be taken with a meal containing fat. If your dinner is your fattiest meal of the day (think olive oil, salmon, avocado, nuts, or cheese), that makes evening the practical best time. Taking K2 on an empty stomach significantly reduces absorption. There’s no evidence that time of day itself affects how well K2 works; what matters is the presence of dietary fat.
What to Avoid Taking at Night
Not every supplement belongs in your evening routine. Vitamin B12 has been associated with a stimulating effect that can decrease sleep quality. If you take a B-complex or a multivitamin containing B12, morning is the better choice.
Calcium supplements can also create problems at night if you’re stacking them with other minerals. According to the Mayo Clinic, calcium interferes with the absorption of magnesium, zinc, and iron. If you take both calcium and magnesium, separate them by taking calcium earlier in the day and saving magnesium for the evening.
Putting a Nighttime Stack Together
You don’t need to take everything on this list. The strongest standalone options for sleep are magnesium glycinate and low-dose melatonin, and many people find one of those sufficient. If you want to layer supplements, a practical evening routine might look like this:
- With dinner: Fat-soluble vitamins (K2, if applicable) alongside foods containing healthy fats
- 3 to 4 hours before bed: Melatonin at 0.3 to 1 mg, if using it
- 30 to 60 minutes before bed: Magnesium glycinate (200 to 250 mg elemental), L-theanine (200 to 400 mg), or valerian root (400 to 600 mg)
- 30 minutes before bed: Casein protein (20 to 40 g), if training regularly
Start with one supplement at a time so you can tell what’s actually helping. Adding multiple new supplements at once makes it impossible to identify which one is responsible for any changes, positive or negative, in your sleep.