Safety check

SlimSet And Sleep: Does 138 mg Of Caffeine Matter At Night?

By SlimSet Team · Medically reviewed by Dr. Dean Tomlin, Doctor · Last updated October 26, 2026 · 8 min read

If you ask how SlimSet and sleep fit together, the answer starts with one number printed on the bottle: 138 mg of caffeine anhydrous in every capsule. This page explains what the research on caffeine and sleep found, why the time you take the capsule matters more than anything else, and how to check your own nights.

What does SlimSet and sleep come down to?

It comes down to caffeine. Caffeine is the only compound on the SlimSet panel present at an amount known to affect sleep. One capsule carries 138 mg of caffeine anhydrous, and the green tea row adds a few milligrams more. The green coffee row adds a small amount the label does not print.

Researchers who reviewed the safety literature found no consistent harm in healthy adults at up to 400 mg of caffeine a day, from every source together. One capsule is a little over a third of that. That is a useful fact. It does not mean the capsule leaves your sleep alone, because the question for sleep is not only how much but when.

What did the research find about caffeine and sleep?

The key trial gave people 400 mg of caffeine at bedtime, three hours before bed and six hours before bed. It measured disruption in all three groups. The six hour group is the one to remember. Those people did not report a problem, yet the measurements showed one.

A wider review of studies reaches the same conclusion. So how you feel at ten at night is not a reliable test. The better test is the timing itself. Our post on what 138 mg of caffeine does covers the dose in more detail.

Note the size of the dose. The trial used 400 mg, which is nearly three SlimSet capsules at once. The capsule gives you less. But the trial was in healthy volunteers, and no study of the finished SlimSet capsule on sleep exists. So the careful reading is simple: do not assume a late capsule is harmless.

SlimSet and sleep: what is known, and what is not?

Source: the side effects, how to use and who it’s for pages of this website.

When should you take SlimSet for the best sleep?

The label says: take one capsule daily with an 8 oz glass of water, and for best results take it 20 to 30 minutes before a meal. It does not name which meal. The seller’s pages narrow it to the morning, but the bottle itself does not.

This website’s advice goes beyond the label here, and says so: choose the earliest meal of your day. An early capsule removes the question. If you are travelling, take it after you wake, whichever time zone you are in. Flying east is harder, since your usual hour may land in the local afternoon.

Take it with the full glass of water the label asks for, not with a second cup of coffee. The label asks for the 8 oz twice in one sentence, which hints at how much it matters.

How can you keep a SlimSet and sleep record?

Write it down. It takes a minute a day and it is the only way to know. The site suggests this simple routine.

1. Before the first capsule, list the caffeine in a normal day: coffee, tea, cola, energy drinks and any pre-workout.
2. For the first week, note your bedtime, your waking time and how the afternoon went.
3. Take the capsule at the same time every day, early.
4. After the first week, compare your notes with the week before you started.
5. If sleep has got shorter or lighter, move the capsule earlier or stop and use the guarantee.

Tolerance matters too. The lift from a steady daily dose tends to fade over a few days, so the lift in week three is not the lift of day one. Early nights and later nights are different measurements, so write down both.

Who should be careful with SlimSet and sleep?

The who-it’s-for page lists someone who sleeps badly and is trying to fix it as a poor fit. Its reasoning is blunt: a stimulant added to a sleep problem works against you, at any hour. Someone who takes no caffeine at all should also be careful, because that person will notice 138 mg. Pick a quiet morning for the first capsule.

Anyone already running a pre-workout or an energy drink should count first. The ledger on the site shows a 12 oz brewed coffee at roughly 120 to 180 mg, a 16 oz energy drink at roughly 150 to 200 mg and a pre-workout scoop at roughly 150 to 300 mg. Those are ranges, not measurements. Read the tub or the can.

Frequently asked questions

Our view

Our view is that SlimSet and sleep is a timing question, and timing is the easiest part to control. Take the capsule early, count your other caffeine and keep a one-week note. That costs nothing and answers the question for you.

If you are already struggling with sleep, or you are sensitive to caffeine, this is not the product to start with. If you take medicines, talk to your doctor first and bring the figure from the label: 138 mg of caffeine anhydrous. Our page on who SlimSet is right for, the side effects page and the home page have more.

Last updated October 26, 2026. Reviewed by Dr. Dean Tomlin, Doctor on the same date.

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