Lab Tests to Consider If Your Metabolism Feels Different in Midlife
If you feel like your metabolism has changed suddenly, you are not imagining it.
Many people in their 40s, 50s, and 60s experience:
Unexplained weight gain
Stubborn belly fat
Sugar cravings that feel new or intense
Energy crashes
Clothes fitting differently even though habits have not changed
Weight loss plateaus that do not respond to eating less or exercising more
These are not motivation problems. They are often physiology problems.
In midlife, changes in hormones, thyroid function, insulin sensitivity, inflammation, stress hormones, and nutrient status can significantly alter how the body regulates weight, hunger, energy, and recovery. Lab testing helps identify whether there is an underlying metabolic reason your body is responding differently than it used to.
Below are the lab tests I most often review when a client says, “Nothing I used to do works anymore.”
Why Lab Testing Matters in Midlife
As we age, the body becomes less metabolically flexible. Blood sugar regulation, hormone signaling, and stress responses shift, even in people who have eaten well and stayed active for years.
If you are experiencing persistent plateaus or symptoms that feel out of proportion to your habits, lab work can help determine whether:
Your body is becoming more insulin resistant
Thyroid signaling is suboptimal
Chronic inflammation is interfering with fat loss
Stress hormones are driving fat storage
Nutrient deficiencies are slowing metabolism and recovery
These issues often develop gradually and may not be identified with basic annual lab panels.
Fasting Glucose and Hemoglobin A1c
Fasting glucose and hemoglobin A1c provide information about blood sugar control over time.
Fasting glucose reflects baseline blood sugar after an overnight fast. Hemoglobin A1c represents average blood sugar levels over the previous two to three months.
Values that are technically within the normal range can still contribute to:
Increased hunger and cravings
Energy fluctuations
Easier fat storage
Difficulty losing weight
This is especially common in perimenopause and midlife, when hormonal changes affect how the body handles carbohydrates.
Fasting Insulin
Fasting insulin is one of the most important markers for understanding metabolic health and weight regulation.
It is possible to have normal glucose and A1c while insulin levels are elevated. This indicates that the body is producing more insulin than necessary to keep blood sugar stable.
Elevated fasting insulin is often an early sign of insulin resistance and is strongly associated with:
Stubborn weight gain
Increased abdominal fat
Frequent hunger
Strong carbohydrate cravings
Identifying elevated insulin early allows for targeted nutrition strategies that support metabolic health.
Lipid Markers That Provide More Information Than LDL Alone
A standard cholesterol panel often does not fully capture metabolic and cardiovascular risk. In midlife, additional lipid markers can provide important insight.
Triglycerides
Elevated triglycerides are commonly associated with insulin resistance and increased visceral fat. They often reflect how the body processes carbohydrates and sugars.
Apolipoprotein B (ApoB)
ApoB measures the number of atherogenic lipoprotein particles. Cardiovascular risk can be elevated even when LDL cholesterol appears normal.
Lipoprotein(a)
Lipoprotein(a) is a genetically influenced marker that increases cardiovascular risk independently of lifestyle factors.
Looking beyond LDL helps clarify how fat metabolism, blood sugar regulation, and inflammation interact in the body.
Thyroid Testing Beyond TSH
Thyroid hormones play a direct role in metabolic rate, energy production, digestion, and weight regulation.
A full thyroid panel provides more information than TSH alone and typically includes:
TSH
Free T4
Free T3
Thyroid peroxidase antibodies
Thyroglobulin antibodies
Suboptimal thyroid patterns can contribute to fatigue, cold intolerance, slowed metabolism, digestive changes, and weight gain, even when TSH is within range.
Not all thyroid imbalances require medication. In many cases, nutrition, stress management, and targeted lifestyle strategies can improve thyroid signaling and symptoms.
Vitamin D, Vitamin B12, and Ferritin
Nutrient deficiencies are common in midlife and can significantly impact metabolism and energy levels.
Low vitamin D, vitamin B12, or ferritin (a blood protein that reflects your body’s iron stores) can contribute to:
Persistent fatigue
Poor exercise tolerance
Slower metabolic rate
Impaired recovery
Increased cravings
These markers are often overlooked but can meaningfully affect how the body responds to nutrition and movement.
hs-CRP and Chronic Inflammation
High-sensitivity C-reactive protein is a marker of low-grade, chronic inflammation.
Even mildly elevated levels can interfere with:
Insulin sensitivity
Hormone signaling
Appetite regulation
Recovery from exercise
Chronic inflammation can make weight loss feel unusually difficult and unpredictable, even when calorie intake is appropriate.
Cortisol and Stress Hormone Patterns
Cortisol patterns often change in midlife, particularly during perimenopause.
Disrupted cortisol rhythms can contribute to:
Increased abdominal fat storage
Sleep disturbances
Afternoon energy crashes
Increased sugar cravings
Salivary cortisol testing at specific points during a 24 hour period allows for assessment of daily cortisol patterns rather than a single point in time. This can be useful when stress appears to be driving symptoms.
How This Information Is Used
The lab testing discussed here is not about diagnosing a disease (dietitians don’t do this work!). It is about understanding what exactly is going on at a subclinical level and contributing to symptoms and plateaus.
When these markers are addressed through individualized nutrition, lifestyle, and stress management strategies, weight loss often becomes more consistent and sustainable. More importantly, addressing these markers leaves you feeling better - less fatigue, better digestion, clearer skin, and so much more.
You cannot mindset your way out of metabolic dysfunction. You have to understand what is happening beneath the surface.
Next Steps
If your metabolism feels different and progress no longer matches your effort, lab testing may provide clarity.
A complimentary nutrition evaluation call allows us to review your history, identify patterns, and determine whether further lab assessment or targeted support would be appropriate.
No pressure. Just clear direction based on your physiology.