Can a blood test diagnose PCOS?

Polycystic ovary syndrome (PCOS) affects around one in ten women in the UK [1]. This article takes a deep dive into all things PCOS, from the diagnostic criteria of the condition, to common signs and symptoms of PCOS you can look out for, plus, how they may appear in a blood test.

We'll explain:

• Three diagnostic features of PCOS
• What causes PCOS?
• Eleven common signs and symptoms of PCOS
• How can PCOS show up in a blood test?
• Can a blood test diagnose PCOS?

Three diagnostic features of PCOS
 

PCOS is a long-term condition that affects how women’s ovaries work. It’s thought to be a result of genetics, raised androgen levels, and insulin resistance [1].

There are three diagnostic criteria for PCOS:

1. Irregular periods– meaning your ovaries don’t regularly release eggs (also known as ovulation)
2. Excess androgens– high levels of hormones such as testosterone
3. Polycystic ovaries– your ovaries become enlarged and contain many fluid-filled sacs (follicles) that surround the eggs

If you experience at least two of these then you may be diagnosed with PCOS. If you think you have two or more of these, it’s a good idea to ask your doctor for an assessment.

Despite the name, the cysts in polycystic ovary syndrome are actually follicles (these are the undeveloped sacs where eggs would usually develop). And in PCOS, these sacs are often unable to release an egg – preventing ovulation.

What causes PCOS?

The exact cause of PCOS is unknown, but it is related to abnormal hormone levels.

Other factors that are thought to play a role in the cause of PCOS include: 

• Genetics- it is also now believed that PCOS may run in families, and there appears to be evidence of a genetic link [2].
• Inflammation – if you have PCOS, you may have increased levels of inflammation in your body, which has been linked to higher levels of androgens [3]. Being overweight can also affect your inflammation levels.
• Insulin resistance – it has been shown that 70% of women with PCOS have insulin resistance, meaning their cells can’t use insulin properly [4].

We explain practical ways you can support your insulin levels through your diet in our PCOS-friendly diet blog.

11 common signs and symptoms of PCOS
 

There are many different signs and symptoms of PCOS. The tricky thing is, many of these symptoms aren’t exclusive to PCOS and you may not experience all of them. Below are some of the more common symptoms you may encounter.

They are:

1. Irregular or absent periods
2. Difficulty losing weight or weight gain
3. Fatigue
4. Hirsutism (excessive growth of thick, dark hair) or hair loss
5. Acne or oily skin
6. Insulin resistance
7. Fertility problems
8. Acanthosis nigricans (dry, dark patches of skin)
9. Ovarian "cysts"
10. Chronic inflammation
11. Mood changes, low self-esteem, and mental health issues

1. Irregular or absent periods

As we mentioned above, PCOS often causes changes in the menstrual cycle, such as irregular or absent periods.

However, it's important to note that irregular or missing periods don't always mean you have PCOS. They could be due to other conditions such as stress, perimenopause, or thyroid conditions.

2. Difficulty losing weight or weight gain

Many women with PCOS struggle with weight management. The exact figure varies, but studies have shown that between38–88% of women with PCOS are overweight or obese [3]. And obesity has been shown to increase the levels or androgens and insulin that circulate in your body [4].

This is challenging for women both physically and emotionally. To add to this, PCOS itself can make it more difficult to lose weight, and being overweight can worsen PCOS symptoms as well as increase the risk of other health problems [5].

However, exercising for PCOS and a PCOS-friendly diet can help you maintain a healthy weight.

3. Fatigue

Fatigue is one of the most common symptoms you may experience with PCOS.

As well as feeling tired during the day, fatigue might also lead to:

• Difficulty concentrating
• Mood swings
• Headaches

Your fatigue may be due to a hormone imbalance or sleep disturbances, such as obstructive sleep apnoea (OSA). Women with PCOS are twice as likely to develop OSA than women without the condition [6,7]. But there are also numerous nutrient deficiencies and conditions that can contribute to fatigue – a Tiredness and Fatigue Blood Test could help you figure out the cause.

4. Hirsutism and hair loss

PCOS can cause excessive hair growth on the face and body (hirsutism), as well as thinning hair on the scalp [8]. These symptoms are usually caused by high levels of testosterone in the body.

Excess hair growth can occur on the:

• Face
• Neck
• Chest
• Abdomen
• Lower back
• Bottom
• Thighs

Hirsutism can range from mild to severe, but often has a huge effect on your quality of life and self-esteem. You can use the Ferriman-Gallway Score to gauge the severity of hirsutism.

Treatments include weight loss (as this can help balance hormones), contraception, or prescription medication to slow hair growth [8].

5. Acne or oily skin

Raised androgen levels can increase oil (sebum) production in the skin, which may lead to oily skin and acne.

You may notice excess oiliness on the:

• Face 
• Back 
• Chest
• Neck 

Increased oil production can clog pores, contributing to breakouts, which can understandably feel frustrating or distressing.

Fortunately, acne linked to hormonal changes can often be improved with the right approach. This may include a consistent skincare routine, targeted topical treatments, lifestyle and dietary changes, supplements, or medication where appropriate.

Our Skin IQ Blood Test can also provide deeper insight into factors that may be influencing your skin and overall metabolic health, including markers related nutrients such as omega-3s, which research suggests may support hormone balance and inflammation in people with PCOS. This test also comes with an expert skin guide from our clinical team with practical steps and product recommendations.

6. Insulin resistance

As many as 70% of women with PCOS have insulin resistance [4].

Insulin resistance means that the cells in the body are resistant to the effects of insulin. To compensate, the pancreas produces more insulin to maintain a normal blood sugar level.

High levels of insulin cause the ovaries to produce too much testosterone and may also lead to weight gain.

Maintaining a healthy weight is one of the best ways to manage insulin resistance, but with PCOS this isn’t always easy. We’ve written a blog all about a PCOS-friendly diet that may help you.

7. Fertility problems

Doctors sometimes prescribe hormonal contraception to women with heavy or irregular periods to help manage their symptoms [5]. In some cases, these symptoms may be linked to undiagnosed PCOS. Because contraception can regulate bleeding artificially, some women only discover they have PCOS when they stop using birth control and notice their cycles don’t return to normal.

If you are not ovulating regularly due to PCOS, it might take longer to conceive. And if you are not ovulating at all, pregnancy won’t be possible without treatment.

You can get more information about how PCOS and fertility are linked in our blog. But the good news is that many people with PCOS do go onto have successful pregnancies. Lifestyle changes, such as improving insulin sensitivity, reaching a healthy weight where appropriate, and supporting overall metabolic health, can help encourage ovulation. Medications may also be prescribed to stimulate ovulation if needed – so it’s important that you speak with a specialist or your GP if you’ve been trying for a baby for one year (under age 35) or six months (aged 36+).

If you are thinking about trying to conceive, or are early in your fertility journey, understanding your hormone levels, ovulation patterns, and metabolic markers can be an important first step. Our Fertility Buying Guide explains which tests can help you build a clearer picture of your reproductive health and feel more prepared when speaking to your GP or fertility specialist.

8. Acanthosis nigricans

Acanthosis nigricans is when dark velvety patches of skin show up on your neck, groin, or under your arm. It's more common in people with darker skin.

Acanthosis nigricans can help identify whether someone with PCOS has an increased risk for type 2 diabetes mellitus [6]. Acanthosis nigricans may be due to an increased BMI and irregular insulin levels.

Treatment for acanthosis nigricans is through a combination of lifestyle changes and medication to balance your hormones and insulin levels. 

9. Ovarian "cysts"

Despite the name, women with PCOS don’t actually have ovarian cysts in the way most people think. Instead, the ovaries contain multiple small, fluid-filled sacs called follicles. Each one holds an immature egg. These follicles are usually very small (about 2–9 mm) and can be seen on an ultrasound scan.

In PCOS, these follicles don’t always mature properly or release an egg each month (ovulate). That’s what can sometimes make periods irregular or make it harder to get pregnant.

The important thing to know is that these follicles themselves are not dangerous, and they don’t need surgery. They’re simply a sign of how the ovaries are functioning.

10. Chronic inflammation

Chronic low-grade inflammation is common in PCOS. Over time, ongoing inflammation may worsen hormonal imbalance and contribute to some of the symptoms we've mentioned above, like as irregular periods, acne, and fertility challenges. It’s also linked to increased long-term health risks, including cardiovascular disease.

Markers such as high-sensitivity C-reactive protein (hs-CRP) can be used to understand inflammation levels and give a broader picture of your metabolic health.

11. Mood changes, low self-esteem, and mental health issues

With all the PCOS symptoms we’ve explored so far, it’s understandable you may find your mental wellbeing is affected. In fact, studies have shown women with PCOS are twice as likely to experience depression than women without [10,11].

Along with the hormonal imbalance and unpredictable menstrual fluctuations which can contribute to mood changes, there are some mood-related nutritional deficiencies such as vitamin D and B12 which may also affect your mental health. 

If you’re feeling low, overwhelmed, or not quite yourself, support is available. Speaking to your GP may feel daunting, but they’re there to listen and can help you access the right care.

How might PCOS show up in a blood test?
 

There’s no definitive rule for how PCOS blood test results might look. But there are a few biomarkers that are more likely to be abnormal if you have PCOS.

Androgens

Raised androgen levels are one of the key hormonal features of PCOS, and it’s estimated to affect between 60-80% of women with the condition [12].

Typical hormone levels include:

• Testosterone levels with PCOS – may be slightly elevated or at the upper end of the reference range. In some women, it can still fall within normal ranges despite symptoms.
• Free testosterone level with PCOS – is often raised (sometimes due to low sex hormone-binding globulin (SHBG)). This can happen even if total testosterone looks normal.
• Free androgen index with PCOS – this isn’t a hormonal itself. It’s a calculation used to estimate how much active testosterone is available. In PCOS, FAI is often above the upper limit, even if total testosterone alone doesn’t look significantly raised.

SHBG

SHBG is a protein that binds to testosterone in the bloodstream. When testosterone is bound to SHGB, it is inactive.

If levels of SHBG are lower:

• Less testosterone is tied to SHGB
• More testosterone remains free and active
• Symptoms of high androgens may be more noticeable

Insulin resistance, which is common in PCOS, can reduce SHBG levels, indirectly increasing free testosterone.

LH:FSH ratio

Although the LH:FSH ratio isn’t part of the formal diagnostic criteria for PCOS, it’s a pattern often seen on blood tests and can provide helpful context.

Luteinising hormone (LH) and follicle-stimulating hormone (FSH) are released by the pituitary gland in the brain. Together, they regulate your menstrual cycle and ovulation. In women without PCOS, LH and FSH are usually fairly balanced, often giving aa ratio close to 1:1.

What happens in PCOS?

In around 60% of women with PCOS, this balance shifts and the LH:FSH ratio is raised to 2:1 or sometimes 3:1.

You may find that:

• LH levels are normal or slightly raised
• FSH levels are normal or slightly low

This imbalance can interfere with normal ovulation. Higher LH levels stimulate the ovaries to produce more androgens (like testosterone), which can contribute to symptoms such as irregular periods, acne, or excess hair growth.

Please remembers that not everyone with PCOS has a raised LH:FSH ratio and the ratio can vary depending on where you are in your menstrual cycle.

Cholesterol

PCOS isn’t just a reproductive condition, it’s also closely linked to metabolic health.

Women with PCOS have a higher risk of developing cardiovascular disease. One reason for this is that PCOS is commonly associated with insulin resistance, which can affect how your body processes fats.

On a blood test, you might notice:

• Raised LDL cholesterol (bad cholesterol)
• Raised triglycerides
• Sometimes lower HDL cholesterol (good cholesterol)

Weight gain, which can be more common and more difficult to manage with PCOS, may further increase cardiovascular risk. However, it’s important to remember that cholesterol changes can happen even in women with PCOS who are not overweight.

Monitoring your cholesterol levels can help you take early steps to reduce long-term risk, whether through lifestyle changes or medical support.

Blood sugar

If you have PCOS, you have a higher risk of developing type 2 diabetes.

This is largely (again) because insulin resistance is very common in PCOS. Regularly monitoring your HbA1c levels (a measure of your blood sugar levels over that past two to three months) can help you identify changes early, even before symptoms develop..

With PCOS, HbA1c may be:

• Within normal range
• In the prediabetic range
• Occasionally, within the diabetic range

If your levels are high, read about the fastest ways to reduce your HbA1c.

 

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References

1. Polycystic ovary syndrome - Causes. In: nhs.uk [Internet]. 20 Oct 2017 [cited 18 Feb 2026]. 
2. The genetics of the polycystic ovary syndrome | Nature Reviews Endocrinology. [cited 2 Mar 2026]. 
3. Barber TM, Hanson P, Weickert MO, Franks S. Obesity and Polycystic Ovary Syndrome: Implications for Pathogenesis and Novel Management Strategies. Clin Med Insights Reprod Health. 2019;13: 1179558119874042. doi:10.1177/1179558119874042
4. Cassar S, Misso ML, Hopkins WG, Shaw CS, Teede HJ, Stepto NK. Insulin resistance in polycystic ovary syndrome: a systematic review and meta-analysis of euglycaemic–hyperinsulinaemic clamp studies. Hum Reprod. 2016;31: 2619–2631. doi:10.1093/humrep/dew243
5. Krug I, Giles S, Paganini C. Binge eating in patients with polycystic ovary syndrome: prevalence, causes, and management strategies. Neuropsychiatr Dis Treat. 2019;15: 1273–1285. doi:10.2147/NDT.S168944
6. Kumarendran B, Sumilo D, O’Reilly MW, Toulis KA, Gokhale KM, Wijeyaratne CN, et al. Increased risk of obstructive sleep apnoea in women with polycystic ovary syndrome: a population-based cohort study. Eur J Endocrinol. 2019;180: 265–272. doi:10.1530/EJE-18-0693
7. Obstructive sleep apnoea (OSA). In: NHS inform [Internet]. [cited 16 Feb 2026].
8. Excessive hair growth (hirsutism). In: nhs.uk [Internet]. 20 Oct 2017 [cited 2 Mar 2026].
9. BDA. Polycystic Ovary Syndrome – the fundamentals. [cited 25 Feb 2026]. 
10. Sukhapure M, Eggleston K, Fenton A, Frampton C, Porter RJ, Douglas KM. Changes in Mood, Anxiety, and Cognition with Polycystic Ovary Syndrome Treatment: A Longitudinal, Naturalistic Study. Neuropsychiatr Dis Treat. 2022;18: 2703–2712. doi:10.2147/NDT.S385014
11. Dubé-Zinatelli E, Anderson F, Ismail N. The overlooked mental health burden of polycystic ovary syndrome: neurobiological insights into PCOS-related depression. Frontiers in Neuroendocrinology. 2025;78: 101203. doi:10.1016/j.yfrne.2025.101203
12. Wang K, Li Y, Chen Y. Androgen excess: a hallmark of polycystic ovary syndrome. Front Endocrinol (Lausanne). 2023;14: 1273542. doi:10.3389/fendo.2023.1273542