Did you know that caffeine is among the most widely consumed psychoactive substances worldwide?
It’s a drug from the same category of psychostimulants as Cocaine and Methamphetamine.
The levels, doses, health benefits, and side effects of caffeine in a pill form or pure caffeine powder may differ from taking caffeine from a few cups of coffee.
Too much caffeine, especially from caffeine pills, can be detrimental to your health, even life-threatening.
To prevent overdose, learn how long caffeine pills last in your body, what factors typically determine it, and how it may impact your health.
How Long Does It Take for Caffeine Pills to Kick In?
Caffeine pills take about 45 minutes after ingestion to kick in. This means it will take about 60 to 75 minutes for the caffeine pill to enter the bloodstream and reach its full effects.
Depending on the body composition, caffeine effects can wear off between 4 to 8 hours later. It means if you take 200 mg of caffeine at 8 am, half of it will still circulate in your blood at 2-3 pm.
4 Factors That Influence Caffeine Half-Life
How long caffeine sticks around in your system before it gets fully metabolized is individual, but below are some common determinants responsible for it.
1 - The Amount You Take
The doses of caffeine you’re used to consuming influence the time needed for your body to process and eliminate it. The higher the caffeine dosage, the longer its half-life.
One study showed that caffeine might circulate in the bloodstream of people with compromised liver function significantly longer than usual (even for 168 hours). 
Keep in mind that many over-the-counter dietary supplements (like weight loss pills or pain killers), packaged foods (including chocolate and other desserts), and beverages (e.g. tea, soda, beer, energy drinks, and even decaf coffee) contain added caffeine.  
“For reference, a 12-ounce can of a caffeinated soft drink typically contains 30-40 milligrams of caffeine, an 8-ounce cup of green or black tea 30-50 milligrams, and an 8-ounce cup of coffee closer to 80-100 milligrams. Caffeine in energy drinks can range from 40-250 mg per 8 fluid ounces.” - FDA
To stay on the safe side, you need to be aware of all the caffeine sources, so always ensure you check the product labels and follow the dosage instructions when taking caffeine pills.
2 - Your Genes
Genetic factors also influence how long caffeine stays active in your bloodstream, your consumption habits, and the effects of caffeine on your body. 
According to studies, a gene called CYP1A2 is up to 95% responsible for caffeine metabolism, whereas a gene called AHR regulates how CYP1A2 is expressed in the liver. 
People who have any defects or lack of this gene metabolize caffeine longer than others and may be more sensitive or even allergic to this potent central nervous system (CNS) stimulant.
Research has also found that a variation of the gene PDSS2 regulates the speed of metabolizing caffeine and the amount you need to feel its effects. 
3 - Your Tolerance and Sensitivity
Caffeine tolerance determines how individuals react to to the stimulant intake in different doses.
It differs from sensitivity to caffeine, which refers to the ability of your body to metabolize this stimulant depending on your unique genetic predisposition.
As explained, minor changes in the CYP1A2 gene influence how efficiently an individual can process caffeine and eliminate it from the body.
Also, the AHR gene regulating the CYP1A2 gene function, as well as the type of adenosine receptors in someone’s brain, influence a person’s sensitivity to caffeine.
If you lack adequate adenosine receptors, the caffeine molecules can’t bind to them, so you’ll probably be less responsive to its stimulating effects.
4 - How Hydrated and Full You Are
Many people claim that coffee consumption on an empty stomach leads to faster caffeine absorption than drinking coffee with or after a meal.
Similarly, consuming caffeine in pills after a heavy meal may take longer to kick in, and the effects may also be weaker than from caffeinated pills taken on an empty stomach.
Also, a study confirmed slower caffeine absorption at individuals with a full stomach who were given meals hard to digest. 
There are some notable differences between coffee and caffeine pills though.
However, some consumers experience digestive issues when using caffeine pills on an empty stomach.
That’s because your body produces hydrochloric acid during caffeine ingestion, which can irritate your stomach.
Coffee acts as a diuretic, stimulating urine excretion and flushing the sodium from your body along with the water. This may lead to dehydration and mineral deficiency.
Drinking water helps minimize these unwanted effects.
What Is Considered Safe Caffeine Consumption?
This amount hasn’t typically been associated with harmful side effects, including:
- High blood pressure
- Irregular heart rate
- Fast heartbeat
- Sleep problems/insomnia
- Muscle tremors and convulsions
- Mild to severe headaches/migraines
- And other caffeine overdose symptoms, even cardiac arrest and death
How Long Do Caffeine Pills Take to Wear Off?
Caffeine pills may take up to 5 hours on average to wear off, while it takes a caffeine pill around 45 minutes to act after ingestion, reaching its peak concentration after 60 to 75 minutes.
In general, the half-life of caffeine may range between 4 and 8 hours, being 5.7 hours in healthy individuals.
It means if you take 200 mg of caffeine at 8 am, half of it will still circulate in your blood at 2-3 pm.
How long you’ll feel the stimulating effects of caffeine from caffeine pills or other sources is individual. It depends on your health conditions, food, alcohol, other stimulants, and medications you’re taking, your age, genetics, tolerance, and various other elements.
Check out our best caffeine pills buyer's guide.