Most of the health assessments these companies use include questions from three key domains: * Current health: age, weight, sleep habits, smoking, diet, exercise, pregnancy status, etc. * Health goals: lose weight, maintain weight, gain weight, build muscle, etc. * Health concerns: skin, sleep, mental clarity and focus, digestion, heart health, blood sugar, etc. Based on your answers, you'll get two to four recommendations that they think may be the most beneficial for you. Most of these services don't target every little thing with their recommendations because they understand you probably don't want to take 20 pills a day. As an example, a pregnant woman will be recommended a prenatal vitamin, someone who reports struggling with sleep may receive melatonin, and someone on a strict vegan diet will likely be recommended a vitamin B12 supplement. But these quick online quizzes have no way of knowing which nutrients your body is actually short on, so don't take the recommendations you get from them as the absolute truth. Services that include comprehensive testing, like Viome, can adjust your recommendations based on your blood nutrient levels or results of stool testing.