Raising your basal body temperature comes down to increasing your metabolic rate, which is primarily controlled by thyroid hormones and supported by nutrition, exercise, stress management, and sleep. A typical basal body temperature (BBT) falls between 96 and 98°F (35.5 to 36.6°C) when measured first thing in the morning before any activity. If yours consistently runs at the low end or below that range, several practical strategies can help shift it upward over time.
Why Basal Temperature Runs Low
Your BBT reflects your basal metabolic rate, which is the amount of energy your body burns at complete rest. The thyroid gland is the primary driver of that rate. It produces a relatively inactive hormone (T4) that must be converted into its active form (T3) by enzymes found in the brain, muscles, fat tissue, and liver. When this conversion process is sluggish or when the thyroid itself underperforms, metabolic heat production drops and your waking temperature falls.
The system is tightly regulated by a feedback loop between the brain and the thyroid. The hypothalamus senses circulating hormone levels and adjusts its signals accordingly. But this loop doesn’t operate in isolation. It responds to nutritional status, stress hormones, and signals from fat tissue. That means low body temperature isn’t always a straightforward thyroid problem. It can reflect inadequate calorie intake, chronic stress, poor sleep, nutrient deficiencies, or low muscle mass.
Eat Enough Calories, Especially Protein
Undereating is one of the most common reasons for a persistently low BBT. When calorie intake drops too low, the body downregulates thyroid output to conserve energy. Your brain literally dials back the signals that drive heat production. Eating enough to meet your energy needs is a prerequisite for a healthy metabolic rate.
Beyond total calories, what you eat matters. Protein has the strongest thermic effect of any macronutrient, meaning your body generates more heat digesting and processing it than it does with fat or carbohydrates. Research in Nutrition & Metabolism found that for every 1% increase in the protein fraction of a meal, diet-induced thermogenesis rose by about 0.22%. This heat production contributes directly to core temperature. Aiming for protein at each meal (eggs, meat, fish, legumes, dairy) is one of the simplest ways to nudge your metabolic furnace higher throughout the day.
Get the Right Minerals
Three trace minerals are essential for thyroid hormone production and activation: iodine, selenium, and iron. A deficiency in any one of them can bottleneck the entire system.
- Iodine is the raw material your thyroid needs to build hormones in the first place. Iodized salt, seaweed, dairy, and fish are reliable sources.
- Selenium powers the enzymes that convert inactive T4 into active T3. Without enough selenium, you can have adequate thyroid output but still run cold because the hormone never gets activated. Brazil nuts are the most concentrated food source; two or three per day typically cover the requirement. Seafood, eggs, and sunflower seeds also contribute.
- Iron is required by the key enzyme that attaches iodine to thyroid hormones during their synthesis. Low iron is especially common in menstruating women and can quietly impair thyroid function even when iron levels aren’t low enough to cause anemia.
Improving intake of all three together is more effective than addressing just one. Research in the International Journal of Molecular Sciences notes that correcting iodine intake without also ensuring adequate selenium and iron can actually cause oxidative stress in thyroid tissue.
Build Muscle Through Resistance Training
Muscle tissue is metabolically expensive to maintain, which means having more of it raises your resting energy expenditure and, by extension, your baseline heat production. A study in the European Journal of Clinical Nutrition found that nine months of resistance training increased resting metabolic rate by about 5% on average, from roughly 1,653 to 1,726 calories per day. The researchers also found that changes in fat-free mass and thyroid hormone levels accounted for much of the individual variation in results.
This doesn’t require becoming a bodybuilder. Consistent strength training two to four times per week, progressively increasing the load over months, builds enough lean tissue to make a measurable difference. The effect is cumulative and long-lasting as long as you maintain the muscle.
Manage Chronic Stress
Cortisol, the body’s primary stress hormone, directly interferes with thyroid hormone activation. It reduces the activity of the enzyme that converts T4 into T3 in peripheral tissues. Research has confirmed a negative correlation between cortisol levels and circulating T3: the higher the cortisol, the lower the active thyroid hormone. Chronic stress also suppresses the brain signals (TRH and TSH) that tell the thyroid to produce hormones in the first place, through increased somatostatin levels.
The practical takeaway is that no amount of dietary optimization will fully compensate if your stress response is chronically elevated. Strategies that lower cortisol over time (regular physical activity, adequate sleep, breathing exercises, reducing overcommitment) remove a direct brake on your body’s heat production.
Protect Your Sleep and Circadian Rhythm
Core body temperature follows a 24-hour rhythm, dropping to its lowest point during sleep and rising in the hours before you wake. This cycle is tightly coupled with your sleep-wake rhythm. Disrupting it through irregular sleep times, shift work, or poor sleep quality can flatten or delay the normal morning temperature rise.
Keeping a consistent wake time is one of the most effective ways to stabilize your circadian temperature rhythm. Room temperature also plays a role. A slightly cool sleeping environment (around 65 to 68°F) supports the natural nighttime temperature drop, which in turn allows a stronger rebound in the morning. Research in the Journal of Physiological Anthropology found that a room that warms slightly around wake-up time helps advance the natural temperature nadir, leading to a more robust morning rise.
Be Cautious With Thyroid-Stimulating Supplements
Ashwagandha is widely marketed as an adaptogen that supports thyroid function, and animal research does show it can stimulate the thyroid gland to produce more T4. In one study, mice given ashwagandha extract for 20 days showed a 111% increase in circulating T4. But this effect is not always benign. Case reports published in Cureus have documented ashwagandha causing thyrotoxicosis (dangerously high thyroid hormone levels) in humans, including rapid heart rate requiring medical intervention. Some commercially available supplements have even been found to contain thyroid hormone doses exceeding what would be prescribed for hypothyroidism.
If you suspect your low BBT is related to thyroid underfunction, getting your thyroid levels tested is far safer than self-supplementing with compounds that stimulate the gland unpredictably. A simple blood panel measuring TSH, free T4, and free T3 can clarify whether thyroid function is genuinely low.
Hormonal Shifts in the Menstrual Cycle
If you menstruate, your BBT naturally shifts across your cycle. During the first half (the follicular phase), temperatures typically range from 97.0 to 98.0°F. After ovulation, progesterone raises your baseline by roughly 0.4 to 1.0°F for the remainder of the cycle. A consistently low temperature across both phases is more meaningful than a low reading during the follicular phase alone. Tracking your BBT for at least two full cycles gives you a clearer picture of your actual baseline rather than catching it at a naturally low point.
Putting It Together
Raising your BBT is not about any single intervention. It requires supporting the full chain of metabolic heat production: eating enough total calories with adequate protein, ensuring you have the key minerals for thyroid function, building metabolically active muscle, keeping cortisol in check, and maintaining a stable circadian rhythm. Most people with a low BBT who don’t have a diagnosed thyroid condition will find that addressing two or three of these factors together produces a noticeable shift within a few weeks to a few months.