By this point you’ve probably seen athletes from all walks of life running with a big black dot on the back of their arm. It’s a wearable device – a sensor, in fact – called Levels that helps you understand how your body uses carbohydrates (more on this below).

Previously, you could only get specialized health tests on the order of a doctor. Now you can send blood, saliva and urine tests by mail without ever putting on pants. This shift from outpatient testing to home testing is due to advances in sample collection. Whether you send in your samples or go to Quest Diagnostics, the science is basically the same, says Kamal Obbad, co-founder and CEO of Nebula Genomics.

The problem lies in the interpretation of the results. When your doctor orders a lab test, they know your history and look at your data with that in mind. But when an algorithm spits out recommendations into an app (under the supervision of a doctor you’ve never worked with), “be careful not to consider this diagnostic information.” Translation: Don’t make any medical decisions based on a home test. “Talk to an expert about your results if possible.”

You can use these home tests to optimize your diet and fitness so that you feel better and perform better.

1. Levels: Ideal for optimizing the diet

Glucose, which comes from carbohydrates, is your body’s fastest and most accessible form of fuel. Go into a workout without enough in your system and you risk collapsing. This biowearable uses a small sensor (stuck to the top of your arm) to monitor blood sugar 24/7 for two weeks at a time. Manually record workouts and meals through its app, and you’ll see live commentary on their impact on your blood sugar so you can change your habits to feel and perform at your best.

[$399 for one month; levelshealth.com]

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2. Inside Tracker: ideal for fitness and performance information

This blood test (go to a lab or have a technician come to your home) analyzes up to 43 biomarkers involved in energy, metabolism, strength and endurance. Use the DNA test to see how 261 genetic markers influence your athletic potential. From there, the app flags issues and offers personalized interventions – “take one serving of probiotics each day” or “aim for three 20-minute HIIT workouts per week” – that can help you level up. superior.

[From $179; insidetracker.com]

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3. Everlywell: the best for testosterone

The right amount of testosterone flowing through you can be the difference between feeling like a stallion and a mopey zoo lion. High or low T can lead to symptoms like fatigue, depression, and decreased muscle mass, as it influences metabolism, sex drive, muscle production, and fat loss. Spit into a tube, send your sample to the certified lab, and an independent doctor certified by your state’s board of directors will determine if your level is normal. If not, see your own document on the next steps.

[$49; everlywell.com]

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4. Rootine: Ideal for nutritional deficiencies

Take a 10-minute online quiz about your health and fitness habits, then take a home DNA or blood test (or download data from ancestry.com or 23andMe). Rootine’s Medical Grade Genetics Lab will analyze 52 genetic markers that studies show impact how your body processes nutrients. Based on your genetic needs, the company will develop a personalized micronutrient formula containing up to 18 vitamins and minerals. Remember that supplements should not be used in place of a healthy diet.

[$69 per month for 3 months; rootine.co]

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5. Thorne: the best for fertility

Crashed reproductive hormones can cause unexplained weight gain, sleep problems, mood swings, fatigue, etc., issues that affect people beyond those who are trying to conceive. Send your saliva sample and blood test in the mail, and certified labs will analyze hormone levels, thyroid function, and stress responses to provide you with a personalized health plan based on your results (think tips such as “focus on resistance training in the morning” or “choose a Mediterranean diet”). Beware of supplement recommendations; since these are not federally regulated, you should always discuss them with your doctor.

[$300; thorne.com]

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