Toenails as health indicators: experts explain what brittle, yellow nails reveal

Nails are more than a cosmetic detail, according to Britain’s top nail experts, who say brittle, yellow or peeling toenails can reflect body-wide health signals. In interviews and product guidance, pedicures, dermatology-savvy nail technicians and beauty founders describe how persistent changes may point to vitamin deficiencies, thyroid function issues, circulation problems or even early diabetes. While not every nail change signals a medical crisis, professionals urge a cautious, evidence-based approach to any unusual pattern and suggest seeking medical advice when signs persist.

Brittle or peeling nails can suggest vitamin deficiencies or thyroid imbalances, while slow nail growth, bluish nail beds or clients with cold hands can sometimes point to circulation problems or, in rare cases, early signs of diabetes. If anything unusual crops up, experts say, it’s prudent to consult a health professional. More common concerns include yellow discolouration—often from wearing dark polishes without a base coat—and nails lifting from the bed (onycholysis), which can be caused by acetone overuse, allergies to gel products or poor removal technique. Keeping nails nourished at the cuticle and around the nail bed is deemed essential for a healthier appearance, with daily care routines highlighted as a simple yet impactful measure.

Leading names in the industry emphasize that nails can offer clues beyond superficial appearance. Rebecca Crawforth, founder of Navy Professional, notes that changes in nails can reflect broad health trends: "Brittle or peeling nails can suggest vitamin deficiencies or thyroid imbalances, while slow nail growth, bluish nail beds or clients with cold hands can sometimes point to circulation problems or, in rare cases, early signs of diabetes. If anything unusual like this crops up, I would always advise seeking medical advice. More common problems include yellow discolouration, often from wearing dark reds or strong polishes without a base coat, and nails lifting from the bed (onycholysis), which can be caused by acetone overuse, allergies to gel products or poor removal technique. How to get youthful-looking nails on older hands? Well-nourished cuticles and skin instantly make nails look fresher. I always recommend massaging our Hand & Cuticle Serum daily, and a gentle exfoliation once or twice a week with a hand scrub keeps hands smooth and bright."

Award-winning brand founder Leighton Denny MBE adds that aging also shapes nail appearance. He explains: "Vertical nail ridges—furrows in the nail that run from tip to cuticle—are like wrinkles, part of the natural ageing process that deepen with age due to slower cell turnover and lack of oil. They become more prominent in menopause due to a drop in oestrogen which can weaken the nail keratin. It’s rare to see spoon-shaped nails, which curve upwards and inwards, but when I do, I always recommend clients see a health professional – it can be a sign of iron deficiency and anaemia. Having beautiful nails is not about length, it’s about health. Nourish nails back to health with my Nail Rebirth Intensive Nail Repair Capsules."

Margaret Dabbs, a leading luxury beauty expert, emphasizes that toenail changes can signal underlying health conditions, with fungal nail being the most common diagnosis. She describes nails that become yellow, thick, crumbly with possible odour or debris underneath, a pattern frequently seen in people with sweaty feet, poor foot hygiene, diabetes or a weak immune system. Her clinic has launched the Nail Fungus Laser Device and related products to support treatment prescribed by podiatrists. Dabbs cautions readers to watch for dark or black streaks, which could indicate trauma but, if persistent, may signal melanoma. Blue or purple nails can indicate poor circulation, Raynaud’s phenomenon or reduced oxygen levels, while pitting may point to psoriasis or eczema. "Watch for changes, but don’t panic at every fluctuation," she advises.

Claire Aggarwal, CEO of Bio Sculpture UK, highlights that dark lines on nails can signal low vitamin D in some cases, though not all changes denote something serious. White marks are often trauma-related, caused by knocks, improper gel removal, or over-filing. As nails age, they may lose strength and shine, but proper treatments can make a meaningful difference. Aggarwal notes the Lavender Base as a product to help restore weak nails and encourage growth, paired with a glossy finish option to achieve a healthier look.

The broader message from the experts is that nails act as a window into overall health. While some changes are benign and age-related, others warrant a health check, particularly if new discoloration, persistent ridges, or sudden alterations in thickness accompany symptoms like fatigue, paleness or shortness of breath. Consumers are urged to observe patterns over weeks rather than reacting to isolated incidents, and to seek medical assessment when signs are persistent or accompanied by other systemic symptoms.

Nail care routines can support healthier appearance and growth even as people age. Practical steps include maintaining moisturized cuticles, gentle exfoliation, and avoiding aggressive removal techniques that can damage the nail bed. Several experts suggest integrating targeted products into daily regimens—such as cuticle serums, hydrating hand creams and lactic or gentle exfoliants—and to use base coats to reduce yellowing from pigments. For some, medical therapies, antifungal regimens or nutritional adjustments may be advised by healthcare professionals, depending on the underlying cause of the nail changes.

In sum, while not every nail change is a medical emergency, the health clues contained in the nails can guide conversations with healthcare providers and help people tailor their skincare and wellness routines. The consensus from the panel is clear: treat nails as part of your overall health picture, and seek expert guidance when changes persist or worsen, especially when they align with other symptoms that could indicate a broader condition.