PCOS: The Blood Tests Behind Irregular Periods
2026-05-12 · 2 min read
Polycystic Ovary Syndrome (PCOS) is one of the most common hormonal conditions in young women — and one of the most confusing, because its signs overlap with so much of everyday life. Blood tests don't diagnose it single-handedly, but they're a big part of putting the picture together.
The signs that bring women in
- Irregular or missed periods, or very long cycles
- Acne and oily skin that won't settle
- Unwanted hair growth on the face or body (or hair thinning on the scalp)
- Weight gain or difficulty losing weight
- Difficulty conceiving
No single symptom means PCOS, and you don't need all of them. That's exactly why testing helps sort it out.
The hormones usually checked
Doctors typically time some of these to specific days of your cycle:
- LH and FSH — the pituitary hormones that direct the ovaries; their balance is often altered in PCOS
- Testosterone (and related androgens) — mildly raised levels explain the acne and extra hair
- Prolactin and TSH — checked to rule out other causes of irregular cycles, since thyroid and prolactin problems can mimic PCOS
- AMH — sometimes used as an ovarian marker
The part people overlook: metabolism
PCOS isn't only about periods — it's closely tied to how the body handles insulin. That's why a good workup often adds fasting glucose, HbA1c and a lipid profile. Catching insulin resistance early matters, because it's linked to the long-term risks of diabetes and heart disease — and it's also the lever that lifestyle changes pull most effectively.
Why testing early is empowering, not scary
PCOS is very manageable, and the earlier it's understood, the more options you have. Weight management, regular activity, the right diet, and — where a doctor advises — specific medication can regulate cycles, calm symptoms and protect long-term health. The blood tests turn a vague, frustrating experience into a clear plan.
A note on timing: because several of these hormones are read against your cycle day, it's worth asking your doctor exactly when to give the sample. Our team can help you book a morning slot or home collection to match.
This article is for general information and is not a substitute for medical advice. Always discuss your results with your doctor.