What are the signs of low vitamin D in women?

Bottom lineLow vitamin D is usually silent; when signs appear they are nonspecific - fatigue, bone or lower-back aches, muscle weakness, low mood, frequent infections, sometimes hair shedding. The pattern that matters is several signs plus risk factors (pregnancy, menopause, PCOS, darker skin, covered clothing, indoor life). A 25-hydroxyvitamin D test settles it: under 30 nmol/L (12 ng/mL) is deficient.

Usually there are none - mild deficiency is mostly silent, which is why it is so common. When signs do appear, they are vague enough to blame on everything else:

The signs worth noticing

• Fatigue that does not match your sleep
• Bone pain or dull aches - classically lower back, hips, or legs
• Muscle weakness, aches, or cramps
• Low mood, sometimes worse in winter
• Frequent infections - vitamin D plays a role in immune function
• Hair shedding in some cases

One of these alone means little. Several together, plus risk factors, is the pattern that justifies a test.

Risk factors that hit women hardest

• Pregnancy and breastfeeding - calcium demand for two
• Menopause - falling estrogen accelerates bone loss, making vitamin D status matter more
• PCOS - deficiency is unusually common alongside it
• Darker skin or covered clothing - both sharply reduce skin synthesis
• Mostly indoor life, higher body weight, or a diet without oily fish or fortified foods

The test and the fix

Ask for a 25-hydroxyvitamin D blood test. Below 30 nmol/L (12 ng/mL) is deficient; 50 nmol/L (20 ng/mL) and above is adequate for most people. If you are low, the fix is boring and effective: sensible sun (see how long that takes), oily fish and fortified foods, and a supplement - 600 IU (15 mcg) is the daily guideline, 4,000 IU the safe ceiling unless prescribed. Check label units with the vitamin D converter, and retest after about 3 months.

The full picture - including severe-deficiency red flags - is in our guide to vitamin D deficiency in women. And if you want to know whether your sun habit is actually producing anything, Femora's Sunshine feature tracks it session by session.

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