Insomnia and nausea may be caused by certain medications, by caffeine overconsumption or by withdrawal from certain recreational drugs. Withdrawal from alcohol and nausea symptoms also share a close relationship, and are often accompanied by insomnia. In some people, insomnia and nausea are side effects of stress. Often, these symptoms are brief and only last for a day or two. Health experts advise, however, that chronic nausea coupled with insomnia may call for a thorough medical examination to determine and treat any possible underlying causes, such as cancer or depression.

Medications, such as Paxil, Prozac, Luvox and Zoloft, which are used to treat depression, may also cause insomnia and nausea. Side effects like these are well-documented and doctors are usually able to address these conditions as they come up individually among patients. Some do not experience these side effects until withdrawing from these drugs, however.

Medicinal herbs that are sometimes abused when used recreationally, such as marijuana, may also cause insomnia and nausea when a heavy user attempts to withdraw from regular usage. For others, withdrawing from alcohol may have the same effect. For serious addicts, withdrawal symptoms can be felt within several hours of the last use of one of these substances.

Individuals who consume high doses of caffeine also frequently experience insomnia and nausea. As a stimulant, caffeine is widely celebrated for its ability to keep people awake and even increase levels of alertness in some individuals. At the same time, however, one of the side effects frequently reported with caffeine consumption is nausea.

Emotional stress is often joined with other symptoms, such as anxiety, muscle aches, headaches, loss of appetite, appetite increases and weight loss. Two of the most common physical symptoms of stress, however, are insomnia and nausea. Often, these are caused by nervousness and anxiety associated with a particularly stressful situation, which prevents a person from sleeping and causes stomach disturbances due to a poor diet. In some people, anxiety and nausea may even be accompanied by vomiting.

When other symptoms are present, such as diarrhea, vomiting, fever or high blood pressure, insomnia and nausea may be the symptom of a more severe condition, such as cancer. Researchers have found more than 20 symptoms that are common to all cancer types at varying stages. Among these physical symptoms, insomnia and nausea have been noted, along with a loss of appetite, fatigue, constipation, weakness, pain and a dry mouth.