SHBG — The Enemy of Active Testosterone

Learn how high SHBG (Sex Hormone–Binding Globulin) can reduce your free testosterone — and what you can do about it. Dr Dan Wright explains the causes, symptoms, and natural ways to rebalance your hormones, including nutrition, lifestyle, and the role of boron.

Many people are told their testosterone levels are “normal,” yet still feel tired, flat, and unmotivated. The missing piece might be SHBG — a liver-produced protein that binds to your testosterone and makes it inactive. In this article, Dr Dan Wright from The Wright Practice, Harley Street, explains how high SHBG can quietly lower your free testosterone, what causes it, and the practical steps to bring it back into balance — from nutrition and exercise to micronutrients like boron.

What is SHBG?

Sex Hormone–Binding Globulin (SHBG) is a protein made in the liver. Its job is to bind to sex hormones, mainly testosterone and oestrogen, and carry them through your bloodstream.

The catch?
When testosterone is bound to SHBG, it becomes inactive. Only the small portion that remains unbound — your free testosterone — can enter cells and do the work it’s meant to do.

Think of SHBG like a taxi service: once testosterone gets in, it can’t get out until the liver says so. Too many taxis, and you’re left with hardly any testosterone free to act.

Why High SHBG Can Be a Problem

When SHBG levels rise, your free testosterone drops — even if your total testosterone looks “normal” on a blood test.
That means you can experience symptoms of low testosterone such as:

• Fatigue and low motivation
• Reduced muscle strength or slower recovery
• Brain fog or low mood
• Low libido
• Difficulty losing body fat

This is why it’s essential to look at SHBG and free testosterone, not just total testosterone, when evaluating hormonal health.

What Causes High SHBG?

SHBG can rise for a number of reasons — some lifestyle-related, others medical:

• Oestrogen dominance (including oral contraceptives or oestrogen replacement)
• Thyroid overactivity (hyperthyroidism)
• Liver conditions
• Aging
• Low insulin levels (common in very low-carb or calorie-restricted diets)
• Nutritional deficiencies (especially zinc and vitamin D)
• Certain medications (anticonvulsants, antiretrovirals)

Sometimes SHBG runs high due to a combination of subtle factors — for example, a lean person on a low-carb diet using oral oestrogen might tick three boxes at once.

How to Naturally Lower SHBG

The key is identifying the cause — but these are the most effective evidence-based strategies:

1. Optimise Nutrition

• Eat enough protein and healthy fats — both help balance hormones.
• Correct zinc and vitamin D deficiencies.
• Don’t be afraid of moderate carbohydrates — extreme low-carb diets can drive SHBG higher.

2. Support Liver and Thyroid Health

Your liver produces SHBG, and your thyroid influences it. Keeping both healthy is essential:

• Avoid excessive alcohol.
• Ensure your thyroid function is checked if SHBG is consistently high.

3. Balance Oestrogen Levels

• If you’re on oral oestrogen, ask your clinician about switching to transdermal (patch or gel) — this can dramatically reduce SHBG.
• Reduce excess body fat, which produces oestrogen in both men and women.

4. Lifestyle Adjustments

• Strength training and resistance exercise naturally boost testosterone and help balance SHBG.
• Prioritise sleep and stress management — cortisol excess can impair testosterone balance.
• Moderate alcohol consumption.

What About Boron?

An interesting area of research involves the trace mineral boron, which may modestly lower SHBG and increase free testosterone.

In small human studies, taking 6–10 mg of boron daily for one week led to:

• A 10–15% reduction in SHBG
• A 20–30% increase in free testosterone
• Mild reductions in oestrogen and inflammation markers

Boron appears to influence how the body metabolises hormones, possibly by improving vitamin D and reducing oestrogenic activity.

However, while the data are promising, boron’s effects are modest and short-term, and long-term safety hasn’t been fully established.
It’s best viewed as a supportive nutrient rather than a main treatment.

Natural sources of boron include:

• Avocados
• Nuts (especially almonds and walnuts)
• Prunes, raisins, and dates
• Wine and certain leafy vegetables

If considering supplements, stay within 3–10 mg per day, and always discuss it with your clinician — particularly if you have thyroid, liver, or kidney issues.

Medical Options (Under Guidance)

In some cases, supplements or therapies can help:

• DHEA – may lower SHBG and improve energy and libido.
• Testosterone therapy – can gradually normalise SHBG when clinically indicated.
• Certain rare medications (like danazol) reduce SHBG but are used cautiously due to side effects.

Always seek medical advice before starting any hormonal or supplement therapy.

The Bottom Line

SHBG isn’t the enemy — but too much of it can block your testosterone from doing its job.

If you feel the symptoms of low testosterone yet your blood results look “normal,” it’s worth checking your SHBG and free testosterone levels.
Balancing these can make a remarkable difference to how you feel, perform, and age.

At The Wright Practice, we take a holistic and proactive approach to hormone health — investigating not just your hormone levels but the factors that influence them.

If you’re experiencing fatigue, low libido, or just don’t feel quite yourself, book a consultation to explore whether SHBG could be part of the story.