Blood biomarkers give objective insights into your health status—including sleep. And the relationship between sleep and your blood biomarkers is bidirectional. So suboptimal sleep can result in unoptimized biomarkers, and suboptimal biomarkers can result in poor sleep. But, some biomarkers are more closely connected to sleep than others.
Here are the biomarkers most related to and impacted by sleep quality and duration.
Magnesium is often called the anti-stress mineral, as it plays a role in relaxing muscles after muscle contraction. Below optimal magnesium levels reduce this relaxant capacity and may lead to muscle cramping. And while the mechanism by which magnesium contributes to sleep isn’t quite understood, low magnesium levels appear to be associated with suboptimal sleep quality. 
If a blood test reveals inadequate magnesium levels, consider increasing your intake of magnesium-rich foods throughout the day or taking a magnesium supplement about two hours before bedtime.
Magnesium supplementation—particularly when used to correct low blood levels— improves sleep by increasing the time you spend in deep sleep, as well as increasing the total time you spend asleep. 
Testosterone is a sex hormone. Optimal testosterone levels are essential for increased bone strength and stimulating muscle mass development. And in both males and females, testosterone helps speed tissue recovery and stimulates red blood cell production. Testosterone also facilitates the body’s recovery processes.
However, research indicates that male testosterone levels and production are intertwined with sleep as the production of the hormone occurs overnight. And testosterone levels in men tend to peak around 5:30 to 8 a.m.  Further research is required to understand this mechanism in females.
Sleeping too much or too little is associated with lower testosterone levels, whereas adequate sleep duration—seven to nine hours of sleep at night—is linked to higher levels. 
If you’re not getting enough sleep during the week, weekend catch-up sleep is also beneficial in improving testosterone status.  Otherwise, shooting for the recommended seven to nine hours of quality sleep each night is essential to achieve or maintain optimal testosterone levels.
Most often, vitamin D is associated with its role in bone health. But vitamin D status is also tied to sleep. Optimal vitamin D levels can improve sleep quality by helping you fall asleep faster and increasing the time you spend asleep.  on the other hand, vitamin D deficiency is linked to suboptimal sleep.
Researchers hypothesize two potential pathways to explain the relationship between vitamin D levels and reported sleep quality. First, vitamin D is indirectly involved in the production of melatonin—a hormone that mediates the sleep cycle. Secondly, vitamin D receptors are involved in brain areas responsible for sleep regulation. 
Getting 20 minutes of sunlight a day and eating vitamin D-rich or fortified foods can help you meet your body’s daily needs for this vitamin. However, if you’re vitamin D status is low or deficient, a supplement may be needed to boost your levels.
Cortisol is often referred to as the "stress hormone." During periods of stress, the body produces cortisol to initiate the fight or flight response—rewiring energy production to fuel the body to handle the current stressor. Cortisol levels naturally fluctuate throughout the day, peaking in the morning to help get you out of bed and declining at night as your body relaxes in preparation for sleep.  This dip in cortisol coincides with an increase in melatonin production.
High levels of stress before bed can cause cortisol levels to remain elevated, making falling an
d staying asleep more challenging. 
Fasting blood glucose and HbA1c
Blood sugar, or blood glucose, is influenced by several factors: carbohydrate intake, stress, and sleep. Both short-term and long-term sleep deprivation are associated with reductions in glucose tolerance and reduced insulin response.  Over time this worsened blood sugar control may lead to chronically elevated blood glucose and HbA1c levels, predictors of diabetes, obesity, and mortality risk.  In addition, a consistent lack of sleep also alters the body’s hunger hormones, increasing appetite. This upregulation of appetite and the impaired insulin response may explain the negative metabolic health outcomes associated with poor sleep. 
hsCRP is a protein closely tied to the immune system’s inflammatory response. And a shorter sleep duration is associated with increased inflammatory marker levels, such as hsCRP. During sleep, many energy-consuming processes, like muscle activity and even breathing, tend to slow down. The body may then divert some of its focus and energy to other processes, like supporting the immune system and resolving lingering inflammation. Less time asleep does not allow for this internal diversion of resources—prolonging or inadequately addressing lingering inflammation and leaving hsCRP levels elevated. [13, 14]
Ferritin is a biomarker of iron storage. Most of the iron stored in the body is bound to ferritin, which makes it a good marker of your body’s iron capacity. 
A sleep-related syndrome, called restless leg syndrome, is exacerbated by deficiencies in iron levels. Restless leg syndrome tends to flare up in the evening, impairing sleep quality. Interestingly, studies show that low levels of ferritin, the storage form of iron, can worsen its symptoms. Therefore, optimizing ferritin levels is crucial. [16, 17] Increase your body’s iron stores by upping your intake of iron-rich foods like lean red meat, seafood, beans, leafy green vegetables, and iron-fortified cereals.
Tack these biomarkers with routine bloodwork
The only way to know whether or not these biomarkers are optimized is with a blood test. And while a yearly physical may capture some of the biomarkers listed here, it likely doesn’t account for them all. Blood biomarkers shift over time, so it's important to track your trends over time.
The InsideTracker sleep goal tracks and analyzes the blood biomarkers associated with sleep mentioned in this article, for example, vitamin D, magnesium, and cortisol. If a sleep-related biomarker is unoptimized on your most recent blood test, you’ll receive science-backed recommendations to improve that biomarker level, which can then improve your sleep. InsideTracker customers can connect their fitness trackers (currently, Oura Ring, Garmin, Fitbit, and Apple Watch) to the InsideTracker mobile app. Those who integrate their fitness tracker unlock deeper, more meaningful insights into their health. The app tracks and analyzes the trends in your sleep—because it’s inevitable for poor nights of sleep to happen. Analyzing these trends over time can help you understand and take action.
Be sure to turn your push notifications on to receive InsideTracker ProTips, nuggets of evidence-based recommendations that are actionable based on your recent data. For example, your sleep duration may indicate that you need to alter caffeine intake, or your deep sleep may demonstrate the benefits of a supplement. Connecting your fitness tracker to InsideTracker can help you make sense of your data and take action. Want to refer back to a previous ProTip? You can view your previous InsideTracker ProTips in the notification center.
Michelle Darian, MS, MPH, RDMichelle is a Nutrition Specialist at InsideTracker. As a Registered Dietitian, you’ll find Michelle analyzing the research behind recent nutrition trends, bringing actionable food and supplement recommendations to the platform. When she's not myth-busting, Michelle can be found exploring new restaurants and getting creative in her kitchen.