Why Diet Pills Can Cause Sleepiness

white and blue medication pill on pink textile

When you think of someone taking often caffeine-fueled diet pills, images of hyperactivity, restlessness and perhaps even insomnia may come to mind. But in some cases the opposite appears to be true.

A plethora of weight loss pills can be found at your local drug store, grocery store and health food outlets. The safety of these dietary supplements is unknown and may be limited because they aren’t thoroughly evaluated as are prescription drugs or over-the-counter medications.

How Diet Pills Work

A variety of ingredients can be found in weight-loss pills. As a general rule, appetite suppressants affect appetite control centers in the brain, causing you to eat less.

Some weight loss tablets and capsules contain more than a dozen herbs, vitamins and minerals as well as caffeine and laxatives. A body’s reaction to this cocktail of ingredients can vary greatly from person to person.

Common side effects of appetite suppressants are irritability, dry mouth, stomach upset or constipation, blurred vision and dizziness.

Why Diet Pills Can Make You Sleepy

Sleepiness can also be a side effect of diet pills. Over-the-counter products that the FDA classifies as weight control drugs are primarily those that contain the active ingredient phenylpropanolamine (PPA). One of the more common side effects of PPA is dizziness or drowsiness.

Many diet pills contain caffeine. Sleepiness can set in when the stimulating effects of this addictive stimulant begin to wear off . Symptoms of caffeine withdrawal can include tiredness, depression, and headaches.

Appetite suppressants that contain the drug sympathomimetic can make someone want to retreat back to bed. Sympathomimetic may cause some people to become lightheaded, drowsy, or less alert than they are normally. Sympathomimetic is typically used on a short-term basis for the treatment of obesity because the body becomes resistant to its action fairly quickly.

Diet Pill Precautions

When using weight reduction aids, make sure to limit your alcohol consumption since it may intensify drowsiness or dizziness. When taking diet pills that contain caffeine, make sure to monitor your daily intake of other caffeinated products such as coffee, soda and chocolate.Take only the recommended dose of the weight loss medication. Contact your doctor if your symptom persist or worsen.

Dietary supplements and appetite suppressants are not subject the FDA regulation as are prescription medications. Over-the-counter weight loss aids can be sold with little evidence of effectiveness or safety.


Diet Information, “Side Effects of Diet Pills”

Mayo Clinic, “Over-the-counter weight-loss pills: Do they work?”

Drugs.com, “Side Effects/Warnings: brompheniramine-phenylephrine-phenylpropanolamine”