Caffeine's strongest effects are felt in the first hour after consuming it, but some effects can last from 4 to 6 hours. Caffeine causes neural excitation in the brain, which the pituitary gland perceives as an emergency and stimulates the adrenal glands to release adrenaline. Caffeine also increases dopamine levels -- the neurotransmitter that is affected by drugs like amphetamines and heroin. Although this occurs on a much smaller scale than seen in other drugs, this may attribute to caffeine's addictive quality.

While caffeine is mildly addictive, it has not been shown to have a direct link with any serious health risks. Still, anyone who's been up all night after drinking too much coffee can tell you that caffeine can affect a person's mood and sleep pattern. Here are some of the frequent effects of caffeine:

Caffeine is a diuretic. Caffeine prompts the body to lose water through urination. This can lead to dehydration and is the reason that caffeinated drinks are not a good idea when working out or doing other activities that require fluids. In fact, it is suggested that you consume an additional 8 ounces of water for every cup of coffee you drink.

Caffeine can cause you to feel nervousness, restlessness, irritability or anxiety. It can temporarily speed the heart rate and raise blood pressure. If you're feeling stressed out, a cup of coffee can actually exacerbate, rather than help, this feeling. Too much caffeine can also hurt a person's ability to concentrate, making it difficult to study.

Caffeine can cause insomnia. It can be very hard to fall asleep when you consume a lot of caffeine. This is especially true if you consume it at night, but is also true of higher doses consumed earlier in the day.

Some caffeinated beverages can have other health effects. For instance, the acid in coffee can upset the stomach, and worsen ulcers. Coffee consumption has also been linked to a possible increased risk of having elevated blood cholesterol. Additionally, the high quantities of sugar found in caffeinated beverages such as energy drinks and sodas can predispose an individual to diabetes and other related cardio metabolic disorders.

Caffeine can have negative effects on a pregnancy. These effects include an increased risk for difficulty conceiving, low birth weight of babies born to people who consumed moderate amounts of caffeine, and miscarriage. Caffeine is transmitted through the placenta and through breast milk to the baby. Therefore, if you're pregnant or thinking about becoming pregnant, the FDA recommends that you stop consuming caffeine or cut back to 1 cup per day.

Remember that caffeine is addictive. If you feel like you can't get going in the morning, feel overly fatigued during the day, or get headaches when you try to stop taking caffeine regularly, these can be signs of dependence.

If you're having trouble sleeping, feel like you are consuming too much caffeine or you don't like the effects of caffeine on your body, here are some suggestions for quitting or cutting back:

• Switch to decaffeinated beverages, or to a mixture of decaffeinated and regular coffee.

• Reduce the number of caffeinated drinks you have every day. If you have coffee in the morning and a Coke in the afternoon, try skipping the Coke and replace it with water or juice.

• Brew tea for a shorter time. The less time you brew it, the less caffeine it will contain. Try herbal teas that don't contain caffeine as well.

• Watch out for soft drinks and energy drinks like Red Bull which can contain added caffeine. This will be listed on the label.

• If you are trying to quit and feel yourself getting a headache, you can try having a small amount of caffeine to alleviate the headache. For some people, this helps keep up the momentum to quit.

• Know what's in over-the-counter medications. These can contain large doses of caffeine, too.

• Drink water or non-caffeinated drinks when you're thirsty. Remember, caffeinated beverages will only add to your body's dehydration. 

Powdered, pure caffeine is being sold in stores and on the Internet.  It is very dangerous given the fact that one teaspoon of pure powdered caffeine is equivalent to the amount of caffeine in about 28 cups of regular coffee. While consumers of caffeinated products such as coffee, tea, and soda may be aware of caffeine’s less serious effects – such as nervousness and tremors – they may not be aware that these pure powdered caffeine products are much more potent and can cause serious health effects, including rapid or dangerously erratic heartbeat, seizures and death. Vomiting, diarrhea, stupor and disorientation are also symptoms of caffeine toxicity.

Most recently, on September 1, 2015, the FDA issued warning letters to five distributors of pure powdered caffeine because these products are dangerous and present a significant or unreasonable risk of illness or injury to consumers.