5 Lab Values Every Woman Over 40 Should Know

Most women over 40 get annual bloodwork done — and most are told their results are "normal." But normal and optimal are not the same thing. As a Clinical Laboratory Scientist with over 20 years of diagnostic experience, I've seen how much information gets lost between the lab report and the patient conversation.

Here are the 5 lab values I believe every woman over 40 should understand — not just whether they're in range, but what they actually mean for your energy, hormones, bones, and long-term health.

1. Ferritin (Iron Storage)

What it measures: Ferritin is the storage form of iron. It's a far more sensitive marker of iron status than serum iron alone.

Why it matters after 40: Low ferritin is one of the most common and most missed causes of fatigue, hair thinning, and brain fog in women — even when hemoglobin is normal. Many women are told they're "not anemic" when their ferritin is actually depleted.

Reference range vs. optimal: Most labs flag ferritin as low below 12–15 ng/mL. However, many functional medicine practitioners and researchers suggest optimal ferritin for symptom-free energy is closer to 50–100 ng/mL.¹

What to ask your doctor: "Can you include ferritin on my next panel?" (It's not always ordered automatically.)

2. Vitamin D (25-OH Vitamin D)

What it measures: The storage form of vitamin D, reflecting your body's overall vitamin D status.

Why it matters after 40: Vitamin D is essential for calcium absorption, immune regulation, mood, and muscle function. Deficiency is associated with increased risk of osteoporosis, depression, and autoimmune conditions — all of which become more relevant after 40.²

Reference range vs. optimal: Labs typically flag deficiency below 20 ng/mL. Many researchers and clinicians consider 40–60 ng/mL to be the optimal range for overall health.³

What to ask your doctor: "What is my actual vitamin D level, and is it optimal — not just sufficient?"

3. Thyroid Panel (TSH + Free T4, ideally Free T3)

What it measures: TSH (thyroid-stimulating hormone) signals how hard your pituitary is working to stimulate the thyroid. Free T4 and Free T3 reflect actual thyroid hormone levels available to your cells.

Why it matters after 40: Thyroid function commonly shifts during perimenopause and menopause. Subclinical hypothyroidism — where TSH is elevated but still "in range" — can cause fatigue, weight gain, cold sensitivity, and cognitive changes that are often attributed to aging or menopause.⁴

Reference range vs. optimal: Standard TSH range is roughly 0.5–4.5 mIU/L. Many thyroid specialists consider a TSH of 1.0–2.0 mIU/L to be optimal for symptomatic women.

What to ask your doctor: "Can we check Free T4 and Free T3 in addition to TSH?"

4. Fasting Glucose (and ideally HbA1c)

What it measures: Fasting glucose reflects your blood sugar after an overnight fast. HbA1c reflects your average blood sugar over the past 2–3 months.

Why it matters after 40: Insulin sensitivity naturally declines with age and hormonal changes. Elevated fasting glucose — even in the "pre-diabetic" range — significantly increases risk of cardiovascular disease, cognitive decline, and metabolic dysfunction.⁵

Reference range vs. optimal: Normal fasting glucose is below 100 mg/dL. Optimal is generally considered below 90 mg/dL. HbA1c below 5.7% is normal; below 5.4% is considered optimal by many longevity-focused clinicians.

What to ask your doctor: "Can we add HbA1c to my panel to get a longer-term picture of my blood sugar?"

5. hs-CRP (High-Sensitivity C-Reactive Protein)

What it measures: hs-CRP is a marker of systemic inflammation. Unlike standard CRP (used to detect acute infection), hs-CRP detects low-grade chronic inflammation.

Why it matters after 40: Chronic low-grade inflammation is a driver of cardiovascular disease, cognitive decline, joint pain, and accelerated aging. Estrogen has anti-inflammatory effects, so as estrogen declines during perimenopause, inflammatory markers can rise.⁶

Reference range vs. optimal: hs-CRP below 1.0 mg/L is considered low cardiovascular risk. Below 0.5 mg/L is optimal. Above 3.0 mg/L indicates high risk.

What to ask your doctor: "Can you add hs-CRP to my next panel? I'd like to understand my inflammation baseline."

The Bottom Line

These five markers — ferritin, vitamin D, thyroid hormones, fasting glucose, and hs-CRP — give you a meaningful window into your metabolic, hormonal, and inflammatory health. They're not exotic tests. Most are available through standard bloodwork. The key is knowing to ask for them, and knowing what optimal looks like — not just normal.

If you'd like help interpreting your own lab results, visit AskSonya.ai for personalized lab analysis. And explore our curated supplement collection for evidence-informed support.

References

1. Camaschella C. Iron deficiency. Blood. 2019;133(1):30-39.
2. Holick MF. Vitamin D deficiency. N Engl J Med. 2007;357(3):266-281.
3. Pludowski P, et al. Vitamin D supplementation guidelines. J Steroid Biochem Mol Biol. 2018;175:125-135.
4. Garber JR, et al. Clinical practice guidelines for hypothyroidism in adults. Endocr Pract. 2012;18(6):988-1028.
5. American Diabetes Association. Standards of Medical Care in Diabetes. Diabetes Care. 2023;46(Suppl 1).
6. Ridker PM. C-reactive protein and cardiovascular disease. J Am Coll Cardiol. 2016;68(20):2250-2252.

This article is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before making changes to your health regimen.