Spring Clean Your Health: 5 Lab Tests to Reset in March

March arrives with longer days, warmer weather, and an undeniable urge to throw open the windows and clean house. But while you're decluttering closets and scrubbing baseboards, there's another type of spring cleaning you shouldn't overlook: resetting your health after winter.

Winter takes a toll on our bodies in ways both obvious and subtle. The body can store vitamin D in fat cells to get through winter, but because we have desk jobs or work inside, and use sunscreen when outside during summer, our bodies struggle to make and store enough to last through the winter months. Meanwhile, hemoglobin A1C levels rise from late fall to spring, while triglycerides are elevated in summer and fall, and high-density lipoprotein decreases steadily from January to December.

Spring gives us a natural reset point. Just as you wouldn't ignore a cluttered room for months on end, your body deserves the same attention after months of indoor living, comfort foods, and reduced activity. These five lab tests can help you understand where your body stands after winter and guide your health decisions for the year ahead.

1. Vitamin D: Your Post-Winter Priority

If there's one test that should top your spring health list, it's vitamin D. According to the National Health and Nutrition Examination Survey (NHANES), roughly half of the U.S. population is vitamin D deficient. After months of limited sunlight and indoor living, your levels are likely at their lowest point of the year.

A lack of vitamin D production by the skin during winter has been linked to Seasonal Affective Disorder (SAD), and research indicates an association between low levels and diseases such as cognitive decline, depression, osteoporosis, cardiovascular disease, hypertension, type 2 diabetes, and cancer. Signs of deficiency include muscle weakness, fatigue, a weakened immune system, and changes in mood and ability to concentrate.

A simple blood test for 25-hydroxyvitamin D can reveal whether your levels are sufficient (generally above 30 ng/mL), insufficient (20-30 ng/mL), or deficient (below 20 ng/mL). If you're considering supplements, knowing your exact level helps determine the right dose. The Food and Nutrition Board recommends adults consume no more than 100 mcg (4,000 IU) per day.

The vitamin D test is particularly valuable in March because it gives you a baseline for the year ahead. With warmer weather and more outdoor time coming, you can see how your natural production improves through spring and summer.

2. Comprehensive Metabolic Panel: Your Body's Status Report

Think of a comprehensive metabolic panel (CMP) as your body's quarterly report. It provides important information about your metabolism (how your body uses food and energy) and the balance of certain chemicals in your body. After months of winter eating patterns and potentially less activity, this broad screening can catch issues before they become problems.

A CMP measures blood glucose, calcium, sodium, potassium, bicarbonate, and chloride. These are electrolytes that help control the amount of fluid in your body. It also checks kidney and liver function, which can be affected by everything from holiday drinking to winter comfort foods to changes in hydration patterns.

Research shows that resting metabolic rate was highest in winter and lower in spring, while spring's milder temperatures might naturally cause a decrease in appetite as people tend to eat less in warmer weather. A spring CMP can reveal how these seasonal changes have affected your body's basic functions.

The comprehensive metabolic panel is especially useful if you're planning diet or exercise changes for spring and summer. It provides a baseline for glucose control, kidney function, and electrolyte balance that can help guide these lifestyle adjustments safely.

3. Thyroid Panel: As Your Energy Returns

As days grow longer and energy naturally starts returning, many people notice their motivation and activity levels shifting. But if you're still feeling sluggish despite the seasonal change, your thyroid might be the culprit.

Research shows that serum TSH levels are highest in January and lowest in May, with TSH levels high in winter and low in summer. Conversely, serum FT3 levels are significantly higher in summer and lower in winter. For healthy subjects, seasonal fluctuation of TSH levels may be an adaptation of energy intake and metabolic rate during different climates throughout the year.

Studies confirm a significant seasonal pattern in thyroid-stimulating hormone levels, with TSH increasing in cold winter-to-spring months and decreasing in summer and fall in both healthy people and those with subclinical hypothyroidism. This means that spring thyroid testing can catch issues that might be masked by normal seasonal variation.

Thyroid problems are surprisingly common, especially in women. Living with hypothyroidism can affect people differently in warm seasons from colder ones, as hypothyroidism slows your metabolism and makes you more sensitive to cold temperatures. If you're still feeling tired, cold, or mentally foggy despite the warmer weather, a thyroid panel can provide answers.

A basic thyroid panel measures TSH, free T4, and sometimes free T3. Given the natural seasonal changes in these hormones, testing in spring provides a good baseline as your body transitions into its higher-energy summer mode.

4. Lipid Panel: After Winter's Comfort Foods

Winter comfort foods have a way of sneaking up on us. Between holiday treats, hearty soups, and cozy dinners, our eating patterns often shift significantly during colder months. Research shows that total cholesterol, LDL cholesterol and non-HDL cholesterol levels are all higher in winter than in summer, with LDL and non-HDL cholesterol 4 mg/dL higher in men and 2 mg/dL higher in women during colder versus warmer months.

As one researcher noted: "In the summer, we tend to get outside, we are more active and have healthier behaviors overall. In the colder months, we tend to crawl into our caves, eat fat-laden comfort foods and get less exercise." Ratios of atherosclerotic risk were lowest in the spring and summer.

A large longitudinal study of seasonal variations in blood lipids found seasonal variations in cholesterol levels both in men and women, with a peak in winter. The seasonal variations were greater in women and hypercholesterolemic individuals. This makes spring an ideal time to check where you stand after winter's dietary changes.

The lipid panel measures total cholesterol, LDL ("bad") cholesterol, HDL ("good") cholesterol, and triglycerides. Spring testing gives you a clear picture of how winter affected your cardiovascular risk factors and helps guide dietary and exercise plans for the warmer months ahead.

5. Hemoglobin A1C: Your Three-Month Blood Sugar Story

Unlike a fasting glucose test that gives you a snapshot of your blood sugar at one moment, hemoglobin A1C tells the story of your average blood sugar over the past two to three months. That means a March test captures how your body handled the entire winter season.

Research consistently shows that in both northern and southern hemispheres, HbA1c is higher in cooler months and lower in warmer months, with hemoglobin A1c higher in cooler months and lower in warmer months in both hemispheres. Studies show A1c values are higher in winter and lower in summer with a difference of 0.22.

This seasonal pattern exists even in people without diabetes. Research in Japan found a difference of 0.5% between winter and spring/autumn in type 2 diabetes patients, attributed to increased caloric intake accompanied by decreased physical activity in winter. In normal years, HbA1c is higher in the winter-spring season and lower in the summer-autumn season.

An A1C test in March provides valuable information whether you have diabetes, prediabetes, or normal blood sugar. If your levels are higher than expected, you'll know that spring and summer lifestyle changes could make a real difference. If they're in a healthy range, you can feel confident about your winter blood sugar management.

Making the Most of Your Spring Health Reset

These lab tests work best as a complete picture rather than isolated data points. Vitamin D deficiency can affect immune function and mood. Thyroid problems can impact metabolism and energy. Blood sugar and cholesterol levels reflect our dietary patterns and activity levels. Together, they tell the story of how winter affected your body and what you might want to focus on as the year progresses.

The beauty of spring testing lies in timing. You're getting results at a natural transition point when motivation is high and the weather is encouraging outdoor activity. If your vitamin D is low, you have months of increased sun exposure ahead. If your cholesterol is elevated, you have a full season of fresh produce and outdoor exercise opportunities. If your thyroid is sluggish, you can work with your healthcare provider on treatment while your body naturally shifts toward its higher-energy summer mode.

Lab testing has also become remarkably convenient. You can order tests online, visit a lab at your convenience, and receive results digitally without needing to schedule a doctor's appointment first. This makes spring health screening more accessible than ever, especially for people who want to be proactive about their health rather than waiting for problems to develop.

Just as spring cleaning leaves your home feeling fresh and organized, spring lab testing can leave you feeling informed and empowered about your health. You're not just guessing about whether those winter months affected your body; you have data to guide your decisions.

Consider this your reminder that health maintenance, like home maintenance, works best when it's proactive rather than reactive. While you're planning garden beds and organizing closets, take a moment to invest in the most important space you'll ever inhabit: your body.